fix(opencode): read opencode's composer bar and footer spinner so a turn can end

An opencode session that ran a tool stayed "working" for good. The running
tool row draws a braille spinner (`⠋ Sleep for 12 seconds...`), which trips
the generic SPINNER_PATTERN and marks the pane working, but only a composer
glyph arms the idle confirmation and opencode declared none, so it fell back
to Claude's `❯`, which opencode never draws. Measured on an isolated
instance: a 16 s turn latched busy/isWorking for the rest of the session.
A text-only turn had the opposite problem and never showed as working.

Measured on live opencode 1.3.0 panes (capture-pane every 250-300 ms through
real turns at 40, 60, 120 and 200 columns, plus the raw PTY stream):

- Every composer row starts with a `┃` bar, and the submitted prompt lands in
  the transcript with the same bar, so a turn's first repaint arms the idle
  check, and tmux's reattach repaint does the same for a restored pane.
- While a turn runs the footer row starts with an 8-cell knight-rider
  spinner, `⬝■■■■■■⬝  esc interrupt`, redrawn about every 40 ms (largest
  gap mid-turn: 121 ms). At rest the TUI is silent and nothing on screen
  draws a `⬝`/`■` run, the 200-column sidebar included.
- The working line is the spinner run, `[⬝■]{8}`, not the label: tmux ships
  `esc` and `interrupt` as separate words joined by cursor moves, so the
  label never reaches the stream detector, and at 40 columns the footer
  wraps it to `esc` / `interr` / `upt`. All 344 spinner chunks of a turn
  match the run after Codeman's ANSI strip.
- A pending permission prompt replaces the composer and stops the spinner,
  so it reads as idle (waiting on the user).
- The last `┃` row on screen is the composer's agent/model row, or the
  permission box's closing bar, never the prompt text, so the submit
  verifier stands down and can never press Enter into a dialog.

Verified on an isolated instance from this branch: a 15 s tool turn emitted
exactly one session:working (+271 ms) and one session:idle (3 s after the
spinner stopped); a permission prompt read idle and the allowed turn went
working -> idle; after a server restart both restored opencode panes (one
at rest, one on a permission prompt) went busy -> idle in about 4 s; a
fresh launch reached an open page as idle in 3 s.

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

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

docs/opencode-integration.md

@@ -920,6 +920,8 @@ const mode = cmd.includes('opencode') ? 'opencode' : 'claude';
 
 > **DEFERRED**: This entire phase (except `waitForOpenCodeReady()`) is out of MVP scope. Idle detection, ANSI content filter, working/busy state tracking, and token parsing are all deferred until we have real PTY output data from stable OpenCode sessions. Only the basic TUI ready detection from `waitForOpenCodeReady()` is needed for the MVP and is included in Phase 3.
 
+> **Update 2026-10-09 (working/idle shipped, from measured data):** the registry entry now declares `capabilities.workDetect` for opencode, measured on a live opencode 1.3.0 pane (pane captures every 250-300 ms through real turns at 40, 60, 120 and 200 columns, plus the raw PTY stream). Every composer row starts with a `┃` bar, which arms the shared screen-probed idle check; a running turn puts an 8-cell knight-rider spinner (`⬝■■■■■■⬝  esc interrupt`) at the head of the footer row, redrawn about every 40 ms, and `[⬝■]{8}` is the working line. The label is not the anchor: tmux ships `esc` and `interrupt` as separate words joined by cursor moves, and below about 45 columns the footer wraps it. At rest the TUI is silent (no cursor or timer redraws), and a pending permission prompt replaces the composer and stops the spinner, so it reads as idle. Before this, a turn that ran a tool latched the session `busy` for good (the tool row's braille spinner tripped the generic spinner detector, and nothing ever armed the idle check). Token parsing and the ANSI content filter remain deferred.
+
 ### Goal
 Detect OpenCode's state from terminal output (idle, working, ready).