fix(session): keep a tab working while Claude waits for its own workers

When Claude hands work to an ultracode workflow or background agents, it
ends its own turn and closes it with `✻ Waiting for 1 dynamic workflow to
finish` instead of `✻ Brewed for 1m 18s`, then resumes by itself when the
workers report back. The pane sits quiet with the composer up, so the idle
probe called the session idle for the whole wait. At phone width the
workflow's progress row also drops its ticking timer, so nothing on screen
changes for minutes.

A new optional registry field, `capabilities.workDetect.awaitingLine`,
names that closing row, and `_probePaneWorking()` counts it as work.
Claude renders the row once from a snapshot and never redraws it, so the
same words stay on screen after the workers finish. `isAwaitingWorkers()`
therefore tests only the newest column-0 row directly above the composer,
never the whole pane and never the PTY stream; a follow-up turn always
puts rows of its own there. The column-0 anchor also keeps an agent from
holding its own tab busy by printing the sentence.

Verified against the live Mac mini pane that reported the bug (2.1.283),
and end to end on an isolated instance: an ultracode session running a
90 s workflow at 46 columns stayed busy through the wait and the
follow-up turn, then went idle 6 s after that turn closed.

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

src/config/cli-registry/schema.ts

@@ -338,6 +338,15 @@ const capabilitiesSchema = z
         // Bounded hard: this is how far up the screen a config file may push the search,
         // and every row it adds is one more row the agent itself may be able to write.
         watchingLines: z.number().int().min(1).max(8).optional(),
+        // Same guard again: tested against a pane row every time a session settles.
+        awaitingLine: z
+          .string()
+          .min(1)
+          .refine(
+            (src) => compileVersionRegex(src) !== null,
+            'awaitingLine must be a regex compileVersionRegex() accepts: at most 200 characters, no nested quantifiers'
+          )
+          .optional(),
       })
       .strict()
       // A window with nothing to search is a typo, not a configuration. Refused at LOAD