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.

docs/rfc/README.md

@@ -31,6 +31,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 | [Multiplex concurrent ACP sessions over one connection](proposed/2026-06-14-acp-multi-session.md) | 2026-06-14 |
 | [Optional Code Mode — model writes TypeScript against an SDK of all tools](proposed/2026-06-15-optional-code-mode.md) | 2026-06-15 |
 | [Runtime schemas for the event vocabulary (Zod vs the merge-extensible-map pattern)](proposed/2026-06-16-typed-event-schemas.md) | 2026-06-16 |
+| [Rich ACP bash rendering — the terminal sub-protocol and command classification](proposed/2026-06-18-acp-terminal-and-tool-rendering.md) | 2026-06-18 |
 
 ## Implemented