fix(acp): address review of the terminal-card alignment (exit parse, background/error, capability snapshot)

Codex + an independent review pass found three real defects in the prior commit:

1. parseExitStatus could misreport a SUCCESSFUL command as a failure: a clean
   exit 0 appends no marker, so output ending in "[exit code: 5]" (no trailing
   newline) was read as the marker. Anchor the parse to a LEADING newline —
   renderResult always inserts one before a real marker, so a body that merely
   ends in marker-like text no longer matches. A narrow residual (a clean exit 0
   whose final line is exactly the marker) is inherent to the replay-only-sees-
   text design and documented; the complete fix (a structured exit on the event)
   is the RFC's named escape hatch.

2. A run_in_background start and an isError result were rendered as exited
   terminal cards with a false exit-0 pill. A background start returns a task-id
   ack (not a streamed terminal) and is no longer marked terminal; an isError
   result (spawn failure / abort) carries no exit pill.

3. The terminal capability was re-read live on the result path, so a second
   initialize between a call and its result could desync them (orphan
   terminal_output or clobbered card). Snapshot the capability per session at
   creation (SessionRecord.terminalEnabled) so call and result always agree.

Also reword the reference-parity claim: keeping the description as a content
block in terminal mode is a DELIBERATE divergence (claude-agent-acp drops it).
Tests added for each; with-key e2e still green.

packages/tool-bash/README.md

@@ -34,7 +34,7 @@ The owning agent is recorded per task id at spawn and kept for the lifetime of t
 
 ## UI presentation
 
-These tools own how their calls render in a UI (an editor's tool-call card) via the `dsh-tools` `presentCall`/`presentResult` seam — a UI never special-cases tool names. For `bash`: the **title** is the exact `command` ("ls -la src") and `kind` is `execute` (terminal/run treatment), matching the reference ACP adapters (claude-agent-acp, codex-acp), which both use the bare command as an execute tool's title. The command is ALSO the **rawInput** for non-terminal UIs that render it (an execute-kind card hides rawInput — Zed shows it only for non-terminal tools — so the command must BE the title to be seen). The model-written `description` rides as a **content** text block shown ABOVE the card (a terminal card has no description slot, so it sits over the command; claude-agent-acp likewise surfaces the description as a separate content block). The completed output is wrapped in a fenced ` ```console ` block as the no-terminal-capability fallback — a UI-only affordance, so the model-facing result text stays unfenced. `bash` also flags itself as a **terminal** (the neutral `terminal` field: `presentCall` sets a `cwd` from the model `workdir` when given — absolute as-is, relative for the UI bridge to resolve against the session cwd — else leaves it for the bridge to fill from the session cwd; `presentResult` carries the raw output plus the parsed `exitCode`/`signal`) so a capable client (Zed) renders a terminal card with an exit-status pill instead of the text block — see `packages/acp` ("Terminal card"). `bash_output`/`bash_kill` present a task-scoped title ("Read output from background task bash-3" / "Kill background task bash-3") with the task id as rawInput. These methods are pure/display-only (they also run on `session/load` replay), and a malformed/older logged arg shape falls back to a generic presentation rather than throwing. See `packages/tools` ("Tool-owned UI presentation") and `packages/acp` ("Terminal card" / "Tool-call presentation").
+These tools own how their calls render in a UI (an editor's tool-call card) via the `dsh-tools` `presentCall`/`presentResult` seam — a UI never special-cases tool names. For `bash`: the **title** is the exact `command` ("ls -la src") and `kind` is `execute` (terminal/run treatment), matching the reference ACP adapters (claude-agent-acp, codex-acp), which both use the bare command as an execute tool's title. The command is ALSO the **rawInput** for non-terminal UIs that render it (an execute-kind card hides rawInput — Zed shows it only for non-terminal tools — so the command must BE the title to be seen). The model-written `description` rides as a **content** text block shown ABOVE the card. (claude-agent-acp DROPS the description in terminal mode and shows only the card; surfacing it as a content block is a deliberate divergence — we keep the human summary visible alongside the card.) The completed output is wrapped in a fenced ` ```console ` block as the no-terminal-capability fallback — a UI-only affordance, so the model-facing result text stays unfenced. A FOREGROUND `bash` run also flags itself as a **terminal** (the neutral `terminal` field: `presentCall` sets a `cwd` from the model `workdir` when given — absolute as-is, relative for the UI bridge to resolve against the session cwd — else leaves it for the bridge to fill from the session cwd; `presentResult` carries the raw output plus the parsed `exitCode`/`signal`) so a capable client (Zed) renders a terminal card with an exit-status pill instead of the text block — see `packages/acp` ("Terminal card"). A `run_in_background` call is NOT a terminal (it returns a task id immediately and never streams a terminal — poll with `bash_output`), and an `isError` result (spawn failure / abort) carries no exit pill (there is no real process exit); both render as the ordinary execute card / fenced text. `bash_output`/`bash_kill` present a task-scoped title ("Read output from background task bash-3" / "Kill background task bash-3") with the task id as rawInput. These methods are pure/display-only (they also run on `session/load` replay), and a malformed/older logged arg shape falls back to a generic presentation rather than throwing. See `packages/tools` ("Tool-owned UI presentation") and `packages/acp` ("Terminal card" / "Tool-call presentation").
 
 ## Background completion notices