fix(web): bound the SGR state and follow real terminal widths

Nine findings, one critical. Terminal cases verified in a real terminal first.

CRITICAL: cells held the accumulated SGR history, so every state boundary
re-emitted the whole chain — output switching color without a full reset
emitted O(n^2) characters. Measured: 3200 such cells produced 25 MB, and the
reviewer's ~90 KB alternating-color case is well under bash's own output cap.
State is now a normalized record (foreground, background, attribute set) with
one canonical sequence per boundary, so the emitted text is linear in cells;
the 90 KB case parses in 36 ms. That also makes the attribute closers every
chalk-based tool writes actually close: `\x1b[1mbold\x1b[22mplain` leaves the
following write PLAIN, which a real terminal confirms.

Width follows emoji presentation, not the U+2600-U+27BF block: `A✓B` redrawn
with `XY` shows `XYB`, so the check every progress line writes is ONE column.
Taking the block as wide misaligned exactly the output this card exists for.

Writing over either half of a wide pair blanks the other, since a terminal
cannot leave one cell of a two-cell glyph standing.

`line\n\x1b[0m` does not end in a newline as a string yet its last parsed line
holds nothing visible, so the terminator check now reads the parsed lines — it
had added a blank row and inflated the collapse count.

A line with no cursor movement no longer builds a column buffer at all; only
its SGR is folded, so an `ls -R` or a 5k-line log allocates nothing per
character.

The `.terminalDescription` rule had been inserted into an existing grouped
selector, silently giving `.codeBody` description typography and changing its
bottom margin from 4px to 0 — a pre-existing surface this PR does not own.
Split out, `.codeBody`'s margin restored.

Three comments contradicted their code: the fixture's exit-marker line (still
claiming recovery from a marker deliberately removed), `bash-sample`'s header
(still routing a click to the details panel, and calling the consumer's cap the
block's own), and a DetailsPanel comment stacked above the wrong rule. The
ui-primitives README documented only the CR/BS half of the replay, so a reader
would expect `OK0%` where `100%\r\x1b[KOK` renders `OK`.

packages/client/ui-conversation/src/client/chat/ToolRow.module.css

@@ -182,14 +182,16 @@ button.leading {
    also replaces each primitive's own standalone vertical spacing with the
    flow's row rhythm. */
 .codeBody,
-/* Indented to the terminal body's own column, so the description reads as the
-   card's heading rather than as another summary row. */
+.terminalBody {
+  margin: 4px 0 4px 22px;
+}
+
+/* Indented to the body's own column so the description reads as the card's
+   heading rather than as another summary row, and sits tight against the card
+   below it. Its own rule: grouping it with a body would put description
+   typography on a `CodeBlock` wrapper and change that body's spacing. */
 .terminalDescription {
   margin: 4px 0 0 22px;
   color: var(--dsw-alias-label-secondary);
   font: var(--dsw-font-xs-13);
 }
-
-.terminalBody {
-  margin: 4px 0 4px 22px;
-}

packages/client/ui-conversation/src/client/skeleton/DetailsPanel.module.css

@@ -93,8 +93,6 @@
   color: var(--dsw-alias-state-error-primary);
 }
 
-/* The terminal card sits directly under its section label, so it drops the
-   primitive's standalone vertical margin; the section owns the spacing. */
 /* Above the card, which is where the render-intent contract puts a terminal
    call's description; the panel has no summary row to carry it. */
 .terminalDescription {
@@ -103,6 +101,8 @@
   font: var(--dsw-font-xs-13);
 }
 
+/* The terminal card sits directly under its section label, so it drops the
+   primitive's standalone vertical margin; the section owns the spacing. */
 .terminal {
   margin: 0;
 }

packages/client/ui-conversation/src/client/toolviews/bash-sample.tsx

@@ -6,10 +6,12 @@
 //
 // A bash call declares the terminal render intent, so this row also renders
 // the command's own output through TerminalBlock. This row has no expand
-// control (a click goes to the details panel), so its terminal body is
-// resident rather than expand-gated as in ToolRow; the block's own height cap
-// (CHAT_TERMINAL_MAX_LINES) and internal expander keep a long output from
-// taking over the message flow.
+// control and is not a details-panel target either (tool rows stopped being
+// one), so its terminal body is resident rather than expand-gated as in
+// ToolRow, and the card's own copy and expand controls are the row's only
+// interactions. CHAT_TERMINAL_MAX_LINES is passed as `maxLines` — the chat
+// flow's tighter cap over the block's own default of 16 — and the block's
+// internal expander keeps a long output from taking over the message flow.
 
 import type { Context } from 'cordis'
 import { IconApiOutline14, StateDot, TerminalBlock } from '@deepseek-ai/dsh-client-ui-primitives'