feat(acp): show the command in execute titles; test via the real bash tool; RFC for terminal rendering

- bash presentCall title is now "description — command" (e.g. "List files in
  src — ls -la src"). An execute-kind ACP card HIDES rawInput (Zed renders it
  only for non-terminal tools), so the command must ride in the always-visible
  title to be seen — matching how claude-agent-acp/codex-acp title execute
  tools. The command stays in rawInput too for non-execute UIs that show it.
- Rework the acp tool-call presentation tests (turns + load replay) to drive the
  REAL dsh-tool-bash + dsh-bash-local via a new makeBridgeHarness({ withBash })
  option, running an actual `echo` — instead of an inline fake bash tool. The
  mock MODEL still scripts the call (deterministic, no key), but the tool and
  executor are real, so the test verifies the shipping presentCall/presentResult.
- AGENTS.md: add the principle "prefer the REAL implementation over a mock/
  stand-in in tests" (mock only the expensive/non-deterministic boundary).
- RFC (proposed): the ACP terminal sub-protocol + command classification — the
  capability-gated rich rendering (live cwd-header terminal card, classify a
  `cat` as a read / `grep` as a search) that the reference adapters do; the
  fenced ```console text block stays the no-capability baseline. Studied
  codex-acp, claude-agent-acp, and Zed's renderer to ground it.

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 model-written `description` is the always-visible **title** (e.g. "List files in the current directory"), the exact `command` is the **rawInput** (the verbatim command stays visible in a detail view without crowding the title), `kind` is `execute` (terminal/run treatment), and the completed output is wrapped in a fenced ` ```console ` block — a UI-only affordance, so the model-facing result text stays unfenced. `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` ("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 model-written `description` followed by the exact `command` ("List files in src — ls -la src"), `kind` is `execute` (terminal/run treatment), and the `command` is ALSO the **rawInput**. Why both in the title: an execute-kind card hides `rawInput` (Zed renders it only for non-terminal tools), so the command must ride in the always-visible title to be seen — the reference ACP adapters (claude-agent-acp, codex-acp) likewise put the command in an execute tool's title. The completed output is wrapped in a fenced ` ```console ` block — a UI-only affordance, so the model-facing result text stays unfenced. `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` ("Tool-call presentation").
 
 ## Background completion notices