fix(gemini): read Gemini CLI's composer bar and spinner line so a turn can end

A gemini session stayed "working" for good after its first turn. Its braille
spinner trips the generic SPINNER_PATTERN and marks the pane working, but only
a composer glyph arms the idle confirmation and gemini declared none, so it
fell back to Claude's `❯`, which gemini never draws.

Measured on live Gemini CLI 0.63.0 panes (capture-pane every 300 ms through
real turns with a shell call at 40, 120 and 200 columns, YOLO and default
approval mode, plus the raw PTY stream). The turns ran against a local
stand-in for the Gemini API (GOOGLE_GEMINI_BASE_URL, which Codeman's custom
endpoint support already sets), since the CLI's TUI does not depend on the
backend and no account is needed for it:

- The TUI repaints its whole bottom region every frame, composer included,
  and the composer sits between a `▄` bar and a `▀` bar; the submitted prompt
  is echoed between the same bars. The `▀` bar arms the idle check: every
  repaint carries it, tmux's reattach repaint too. The composer's prompt
  character is no good: it follows the approval mode (`*` in YOLO), and its
  `>` also starts the echoed prompt, which would make the submit verifier
  read a submitted prompt as stranded and press Enter again.
- While a turn runs a line `⠦ Thinking... (esc to cancel, 6s)` animates about
  every 80 ms (largest gap mid-turn: 214 ms). The label can be any loading
  phrase, so the working line is the `(esc to cancel, <n>` suffix, or a
  spinner frame opening a line for when a long phrase wraps that suffix.
  Nothing at rest matches either.
- A tool confirmation (default mode) replaces the composer, stops the
  spinner and the pane goes silent (3.9 s gap), so it reads as idle.

Verified on an isolated instance from this branch: a YOLO turn emitted one
session:working (+170 ms) and one session:idle (2.5 s after the last output);
a default-mode turn went working -> idle while the confirmation waited ->
working once allowed -> idle at the end; after a server restart four restored
gemini panes went busy -> idle in about 4 s; a fresh launch settled in 3 s.

The launch-settle and uncharacterised-CLI tests that used gemini as their
example of a CLI without work detection now use grok and deepseek.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -266,7 +266,7 @@ Scoping needs no check of its own here: `setPaneExit()` already forces `paneExit
 
 So: `_confirmIdle()` (session.ts) requires the pane to go quiet, and then asks the SCREEN via `capturePaneText()` + `CLAUDE_WORKING_LINE_PATTERN` before believing it; a sustained run of repaints (`session-activity.ts`, pure + unit tested) is what marks a turn as started, with the same screen probe vetoing keystroke echo. Idle now lands ~3-5s after a turn ends instead of 2s into one.
 
-⚠️ **The composer glyph and the working line are per-CLI registry DATA** (`capabilities.workDetect`, #385), not Claude constants: claude declares `❯` plus the pattern above, codex declares `›` plus `[Ee]sc to interrupt`, pi declares its composer rule `─` plus the spinner it embeds there, opencode declares its composer bar `┃` plus its 8-cell footer spinner `[⬝■]{8}`, omp declares its input row `╰─` plus the spinner and elapsed time that replace the `π` in its status bar, and a CLI that declares neither falls back to Claude's pair, which is what every session used before the registry carried one. Before that, this whole mechanism was gated Claude-mode-only on the reasoning that an external CLI has no `❯`, which was true and still left every Codex session reporting `idle` for its entire life.
+⚠️ **The composer glyph and the working line are per-CLI registry DATA** (`capabilities.workDetect`, #385), not Claude constants: claude declares `❯` plus the pattern above, codex declares `›` plus `[Ee]sc to interrupt`, pi declares its composer rule `─` plus the spinner it embeds there, opencode declares its composer bar `┃` plus its 8-cell footer spinner `[⬝■]{8}`, omp declares its input row `╰─` plus the spinner and elapsed time that replace the `π` in its status bar, gemini declares its composer's bottom bar `▀` plus its `(esc to cancel, <n>s)` spinner line, and a CLI that declares neither falls back to Claude's pair, which is what every session used before the registry carried one. Before that, this whole mechanism was gated Claude-mode-only on the reasoning that an external CLI has no `❯`, which was true and still left every Codex session reporting `idle` for its entire life.
 
 ⚠️ `workingLine` is config-supplied (a user `clis.json` can set it) and the compiled pattern runs on the PTY hot path, so it goes through `compileVersionRegex()` in BOTH the schema refine and `_workingLinePattern()`: a nested quantifier there is a ReDoS against the event loop, and the helper returns null rather than throwing so the fallback is structural.