fix(web): keep escapes, UNC roots, and truncated cwd honest

Four review findings. Two are defects the previous two rounds introduced,
which the existing tests did not catch:

A backspace erased raw bytes, so one landing after an SGR reset ate part of
the escape: `\x1b[31mabc\x1b[0m\b\bXY` left `\x1b[` and repainted the rest of
the line with whatever the remainder parsed as. Backspaces now resolve over
VISIBLE characters — a CSI sequence is one indivisible unit a backspace steps
over on its way to the last printed character, so the surviving text keeps
the color its run authored.

The cwd normalizer popped a UNC share root: `\\server\share` with a `..`
became `/server`, losing the separators too. A UNC path's server and share
are its root, and Windows cannot climb above a share, so they are split off
and the remainder collapses against that root.

The other two are gaps the earlier fixes left:

The render-site fallback row still passed the args-derived summary, so any
terminal-declaring tool without its own keyed row (`terminal_send`) lost the
contract's above-card description. It now prefers the description exactly as
BashRow does.

A settled call read `call?.cwd`, which cannot tell "the call omitted a cwd"
from "the paging window dropped the call head". The second case has no cwd
anywhere and the original call may have used an explicit workdir, so it now
draws a bare `$` instead of naming the session workspace.

.agents/notes/implemented/feature/2026-07-28-web-terminal-card.md

@@ -12,7 +12,7 @@ The Web client ignored it. `packages/client/ui-conversation/src/client/contract/
 
 ## Decision
 
-`TerminalBlock` is a `ui-primitives` component that renders a shell command as a terminal surface, and both Web render sites for a bash call consume the terminal render intent through it: the chat tool row's expanded body and the details panel's Output section. `ui-conversation/src/client/contract/terminal-card-model.ts` is the single place that turns the snapshot's `callView`/`resultView` pair into the component's props, so the two sites cannot disagree about a command, its cwd, or its exit status. It returns null — the generic path — whenever neither side declares `card: 'terminal'`, including a `card` value this client version does not know, and whenever a settled call's result view is generic, which is how the bash tool's execution errors and background starts keep their existing rendering. Two duties the render-intent contract assigns to the UI bridge land here rather than in the tool: a settled result's `title` REPLACES the pending one, and the working directory resolves against the session workspace — an absolute view cwd is used as-is, a relative one joins under the workspace, and an omitted one IS the workspace, which is the common case for a bash call with no `workdir`. A pure presenter cannot see the session cwd, which is why the resolution belongs at this seam; each render site supplies the cwd off the session list row. The resolved path also normalizes its `.`/`..` segments, because the bash executor resolves the workdir before running: a `..` against `/w/app` runs in `/w`, so the prompt label has to read `w` rather than `..`. The call view's `description` rides the same derivation, since the contract renders it above the card and it must outrank the row's args-derived summary.
+`TerminalBlock` is a `ui-primitives` component that renders a shell command as a terminal surface, and both Web render sites for a bash call consume the terminal render intent through it: the chat tool row's expanded body and the details panel's Output section. `ui-conversation/src/client/contract/terminal-card-model.ts` is the single place that turns the snapshot's `callView`/`resultView` pair into the component's props, so the two sites cannot disagree about a command, its cwd, or its exit status. It returns null — the generic path — whenever neither side declares `card: 'terminal'`, including a `card` value this client version does not know, and whenever a settled call's result view is generic, which is how the bash tool's execution errors and background starts keep their existing rendering. Two duties the render-intent contract assigns to the UI bridge land here rather than in the tool: a settled result's `title` REPLACES the pending one, and the working directory resolves against the session workspace — an absolute view cwd is used as-is, a relative one joins under the workspace, and an omitted one IS the workspace, which is the common case for a bash call with no `workdir`. A pure presenter cannot see the session cwd, which is why the resolution belongs at this seam; each render site supplies the cwd off the session list row. Only a PRESENT call view can mean "omitted, so use the workspace": when the paging window drops the call head there is no cwd anywhere — the result view carries none — and the original call may have used an explicit workdir, so the prompt draws a bare `$` rather than naming a directory it cannot know. The resolved path also normalizes its `.`/`..` segments, because the bash executor resolves the workdir before running: a `..` against `/w/app` runs in `/w`, so the prompt label has to read `w` rather than `..`. A UNC path's `server` and `share` are part of its root rather than poppable segments, since Windows cannot climb above a share. The call view's `description` rides the same derivation, since the contract renders it above the card and it must outrank the row's args-derived summary.
 
 The component's contract:
 
@@ -20,7 +20,7 @@ The component's contract:
 - **One run-state dot for the call, on the first row.** `StateDot` in three of its four states: the chase while running, red for the exit status that also renders the pill, green for a clean settle — the same indicator a tool row's leading icon uses, so a row and its own card cannot disagree about one command. The dot exists because the first question a reader has about a shell command is whether it is still running, and without it that had to be inferred from the absence of output — which a settled command producing no output also looks like. It sits out of flow in a gutter reserved to the left of the card surface, so it neither indents its command nor depends on the command's own text metrics to line up with it. Exactly one dot, whatever the line count: the exit status the view carries is the whole call's, and bash reports no per-command status, so a dot per line would assert of a line that succeeded inside a failing call that the line itself failed. The single visually hidden text label carries the same scope, since `StateDot` is `aria-hidden` and one label per row would read to assistive technology as several distinct outcomes.
 - **No soft wrapping.** Output lines are `white-space: pre` inside a horizontally scrolling box. Column alignment survives; a long line scrolls instead of folding.
 - **Height cap with an expand control.** Output longer than `DEFAULT_TERMINAL_MAX_LINES` (16) lines shows `ceil(max/2)` head lines plus the remaining tail lines, with a button in between that reports the hidden count and expands. The count is of parsed lines after the trailing output terminator is dropped, so an N-line output ending in a newline is N lines. The split arithmetic is the same as the TUI transcript's collapsed tool card (`packages/ui/tui/src/components/transcript.ts`), so one command's head and tail slices agree between the two front ends.
-- **ANSI color.** `anser` splits the SGR runs; `ui-primitives/src/ansi.ts` resolves each run into an inline style rendered as React spans. A foreground-only run maps the basic 16 colors onto `--dsw-*` theme tokens so authored color stays legible under both themes; a run that paints its own background keeps anser's literal rgb for both so its intended contrast survives, as do 256-palette, truecolor, and the two basic colors this design system has no token for. Sequences that carry no color (OSC strings, non-CSI escapes, inert C0 controls) are stripped before parsing so they never reach the DOM as literal characters. Two cursor movements resolve before that strip, because their effect on the visible text has to land before the characters expressing them are dropped: a carriage return reduces its line to the final redraw, and a backspace overwrites the character before it, so `abc` followed by two backspaces and `XY` reads `aXY` as a terminal draws it. Both are per-line, so neither reaches across a newline.
+- **ANSI color.** `anser` splits the SGR runs; `ui-primitives/src/ansi.ts` resolves each run into an inline style rendered as React spans. A foreground-only run maps the basic 16 colors onto `--dsw-*` theme tokens so authored color stays legible under both themes; a run that paints its own background keeps anser's literal rgb for both so its intended contrast survives, as do 256-palette, truecolor, and the two basic colors this design system has no token for. Sequences that carry no color (OSC strings, non-CSI escapes, inert C0 controls) are stripped before parsing so they never reach the DOM as literal characters. Two cursor movements resolve before that strip, because their effect on the visible text has to land before the characters expressing them are dropped: a carriage return reduces its line to the final redraw, and a backspace overwrites the character before it, so `abc` followed by two backspaces and `XY` reads `aXY` as a terminal draws it. Both are per-line, so neither reaches across a newline. A backspace steps over CSI sequences rather than erasing their bytes: a sequence moves no cursor, and eating part of one would corrupt it and repaint everything after with whatever the mangled remainder parses as, so it walks back to the last PRINTED character and drops that instead — the surviving text keeps the color its run authored.
 - **Exit status and copy.** A non-zero exit code or a signal renders a status pill, matching the exit-status distinction the bash tool's own renderer draws; a clean exit renders none, and settled empty output renders a dimmed placeholder. The copy control copies the raw output text, not the rendered tree, so the prompt line and the pill stay out of the clipboard.
 
 Geometry, radius, and fonts mirror `CodeBlock`, so a terminal card and a fenced code block match visually; `white-space: pre` plus horizontal scroll is the deliberate divergence. The clipboard write both components need moved out of `CodeBlock` into a package-internal `src/clipboard.ts`, unexported so it stays an implementation detail of the two blocks.