fix(session): decide working/idle from the pane, not the composer redraw

Every working Claude session reported `status: "idle"` about two seconds
into its turn. Measured on live workers: two sessions mid-tool-call at 13
and 17 minutes both read `idle` while their panes showed
`✻ Actualizing… (13m 23s · ↓ 47.5k tokens)`.

Two things had drifted apart:

1. The working indicator changed. Claude animates the glyph through
   `· ✢ ✳ ∗ ✻ ✽` and randomizes the gerund per turn, so neither
   SPINNER_PATTERN (braille, no longer drawn) nor the keyword list
   (Thinking/Writing/Reading/Running) matches a turn anymore.
2. A `❯` sighting is not the end of a turn. Claude redraws the composer
   roughly once a second all the way through one, and that redraw armed
   the "2s later, call it idle" timer.

Matching the new status line in the STREAM does not fix it either: tmux
ships partial repaints, so the complete line reached the PTY about once
every 20 seconds while the `❯` arrived every second.

So the decision moves off the stream:

- An unbroken run of repaints marks a turn as started. Sampled once a
  second for 12s over six live sessions, the two working ones produced
  output in 12/12 windows and the four idle ones in 0/12. Pure helpers in
  session-activity.ts carry the thresholds.
- Idle now needs the pane to go quiet AND the screen to agree.
  `_confirmIdle()` asks tmux what is rendered (new `capturePaneText()`,
  one plain `capture-pane`, floored at 1.5s per session and only ever at
  a transition) and re-checks every 5s while the screen still shows work.
  A turn can sit silent for tens of seconds inside one tool call, so
  silence alone proves nothing.
- The same screen check vetoes keystroke echo, which is a steady stream
  of repaints too but is not work.

CLAUDE_WORKING_LINE_PATTERN matches the `… (elapsed)` shape rather than
the glyph, because the FINISHED line (`✻ Cooked for 2m 49s`) carries the
same glyph and would otherwise pin a session at working forever.

Claude mode only. An external CLI has no `❯`, so nothing would arm the
confirmation and such a session would latch busy.

respawn-patterns.hasWorkingPattern() had the same blind spot (its gerund
list cannot see "Actualizing"), so it takes the pattern as an extra
signal. That can only make respawn less eager, never more.

Idle now lands about 3 to 5 seconds after a turn ends instead of 2
seconds into one. Verified end to end against a live worker, sampled
against the CLI's own "esc to interrupt" footer as independent ground
truth: busy for all 25s of a turn, idle 3s after it ended.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/utils/index.ts

@@ -17,6 +17,7 @@ export {
   ANSI_ESCAPE_PATTERN_SIMPLE,
   TOKEN_PATTERN,
   SPINNER_PATTERN,
+  CLAUDE_WORKING_LINE_PATTERN,
   stripAnsi,
   SAFE_PATH_PATTERN,
   execPattern,

src/utils/regex-patterns.ts

@@ -60,6 +60,24 @@ export function stripAnsi(text: string): string {
  */
 export const SPINNER_PATTERN = /[⠋⠙⠹⠸⠼⠴⠦⠧]/;
 
+/**
+ * Claude Code's live working status line, e.g.
+ *   `✻ Actualizing… (13m 23s · ↓ 47.5k tokens)`
+ *   `✽ Herding… (3s · esc to interrupt)`
+ *
+ * Matched on the ELLIPSIS + elapsed timer, never on the leading glyph: the
+ * animation cycles through `· ✢ ✳ ∗ ✻ ✽` (two of those are ordinary punctuation)
+ * and the gerund is randomized per turn, while the finished line (`✻ Cooked for
+ * 2m 49s`) carries the same glyph with no `…` and no parenthesis. Feed this
+ * ANSI-STRIPPED data: tmux colours the timer separately, so the raw stream has
+ * escape sequences sitting between the `…` and the `(`.
+ *
+ * A sighting is proof the pane is working; its ABSENCE proves nothing, because
+ * tmux repaints partially and the whole line reaches the PTY only occasionally
+ * (see `session-activity.ts` for what carries the idle decision instead).
+ */
+export const CLAUDE_WORKING_LINE_PATTERN = /…\s*\((?:\d+h\s+)?(?:\d+m\s+)?\d+s\b|esc to interrupt/;
+
 export const SAFE_PATH_PATTERN = /^[\p{L}\p{N}_/\-. ~]+$/u;
 
 /**