fix(omp): read omp's status bar so an omp turn can end

An omp session stayed "working" for good once a turn started, the same
latch pi had: omp's braille spinner trips the SPINNER_PATTERN fast path,
and only a composer glyph arms the idle confirmation. omp declared none,
so it fell back to Claude's `❯`, which omp never draws once its setup
wizard is done.

Measured on live omp 18.8.6 and 18.0.11 panes, holding a turn open
against a local endpoint that never answers: the input row is `╰─ <text>`
and is redrawn at submit, at the end of a turn, at launch and on
reattach. While a turn runs, the status bar's leading `π` becomes a
braille spinner plus the elapsed time (` ⠼ 14s > ⬢ model > ...`; 18.0.11
pads it with two spaces, past a minute it reads `1m`), with a
`⎋ Working…` row above it. The registry entry now names the input row as
the glyph and either working signal as the working line.

The glyph also switches the submit verifier on for omp, which reads the
input row the way it reads Claude's composer. A prompt sent mid-turn goes
to omp's Steering queue and clears the row, so the verifier stands down.
Text left in the row after an Enter is the one case it re-presses.

Verified end to end on a sandboxed instance (own HOME and PATH, omp
18.8.6): session:idle at launch, session:working during a turn,
session:idle about 3 s after it ended, and a restored pane settled idle
about 3 s after a server restart.

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

src/session.ts

@@ -4485,7 +4485,7 @@ export class Session extends EventEmitter {
           : this._mux.capturePaneText?.(this._muxSession.muxName),
       sendEnter: () => this._mux?.sendInput(this.id, '\r'),
       // ⚠ NO fallback glyph here, unlike the screen-reading probe elsewhere in this file.
-      // Only claude, codex, pi and opencode declare a promptGlyph; the other modes would fall back
+      // Only claude, codex, pi, opencode and omp declare a promptGlyph; the other modes would fall back
       // to claude's `❯`, which is ALSO starship's default shell prompt (and pure's, and
       // spaceship's, and p10k lean's). On a shell session the line `❯ npm run build` sits
       // on screen for as long as the command runs, promptStillInComposer() reads that as