fix: repair herdr schema-probe broken pipe and crewmate completion signal

[navidRashik]

Intent

Fix two bugs found live in production: (1) a broken-pipe stderr write in the herdr backend's schema capability probe, and (2) crewmates finishing without appending a terminal done: status, which makes the watcher wedge-escalate finished tasks forever. Each fix ships with a regression test.

What Changed

• bin/backends/herdr.sh: Replaced printf ... | grep with herestring (grep -Fq ... <<<"$schema") in the schema capability probe to eliminate a broken-pipe EPIPE error that occurred when grep exited early on the ~220KB schema payload in SIGPIPE-ignoring watcher environments.
• bin/fm-brief.sh: Added an explicit warning in both crewmate brief templates clarifying that the pane summary is not a completion signal — a missing done: or failed: append causes the watcher to escalate a finished task as a wedge indefinitely.
• tests/: Added two regression tests (fm-backend-herdr-schema-probe.test.sh, fm-brief-done-signal.test.sh) covering both fixes; both pass in CI.

Risk Assessment

✅ Low: Both fixes are narrow and correct: the herestring substitution eliminates the SIGPIPE race without altering grep exit semantics, and the brief reinforcement is a pure textual addition with no behavioral side-effects; both carry well-structured regression tests.

Testing

Ran both regression tests added by the change. The schema probe test exercised a >220KB multi-line fixture under a SIGPIPE-ignored shell, confirmed no broken-pipe error appears, verified the positive control still reproduces the error with the old pipe form, and confirmed the code no longer pipes to grep. The done-signal test scaffolded a real brief and confirmed all three reinforcement phrases are present, plus a static count guard that both status-protocol blocks carry the reinforcement. All assertions passed (ship-brief runtime test gracefully skipped on macOS bash 3.2 due to a pre-existing heredoc-in-command-substitution limitation unrelated to this change).

Evidence: Regression test output

=== Schema probe regression test === ok - fm_backend_herdr_events_capable: large early-matching schema probed without a broken-pipe write error ok - control: the old pipe form still reproduces the broken-pipe write error on this fixture ok - fm_backend_herdr_events_capable: schema markers are searched without piping the payload === Done-signal regression test === ok - scout brief: terminal-status append is reinforced at the status protocol ok - skip: this bash (3.2.57(1)-release) cannot parse fm-brief.sh's ship half (heredoc in command substitution) ok - bin/fm-brief.sh: all 2 status-protocol blocks reinforce the terminal-status append

=== Schema probe regression test ===
ok - fm_backend_herdr_events_capable: large early-matching schema probed without a broken-pipe write error
ok - control: the old pipe form still reproduces the broken-pipe write error on this fixture
ok - fm_backend_herdr_events_capable: schema markers are searched without piping the payload

=== Done-signal regression test ===
ok - scout brief: terminal-status append is reinforced at the status protocol
ok - skip: this bash (3.2.57(1)-release) cannot parse fm-brief.sh's ship half (heredoc in command substitution)
ok - bin/fm-brief.sh: all 2 status-protocol blocks reinforce the terminal-status append

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

✅ **Test** - passed

✅ No issues found.

• bash tests/fm-backend-herdr-schema-probe.test.sh
• bash tests/fm-brief-done-signal.test.sh

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.