fix: reduce crewmate status wake noise

[kunchenguid]

Intent

Reduce firstmate wake noise from crewmate status reporting. The captain observed that crewmates write FYI-ish status lines (e.g. 'installed dependencies', 'attached chrome-devtools-axi') that each wake the supervising firstmate agent for no actionable reason. Tighten the brief scaffold's reporting rule (rule 4 in bin/fm-brief.sh) so crewmates append status lines only on real phase changes a supervisor would act on (setup done, bug reproduced, fix implemented, validation passed) plus the needs-decision/blocked/done/failed states, and explicitly not step-by-step progress - firstmate peeks the tmux pane for that. Deliberate decisions: keep the same status file mechanism and state vocabulary unchanged; the change is wording-only in the scaffold heredoc, no behavior change to any script logic; the rationale sentence 'Each append wakes firstmate' is intentionally included so crewmate agents understand why sparse reporting matters.

What Changed

• Tightened the fm-brief.sh scaffold so crewmates report only supervisor-actionable phase changes plus needs-decision/blocked/done/failed states.
• Added brief wording that each status append wakes firstmate and that step-by-step FYI progress should stay out of status files.
• Documented the sparse crewmate status cadence in AGENTS.md.

Risk Assessment

✅ Low: The branch only tightens wording in the brief scaffold without changing script behavior, and the new guidance matches the watcher/status-file contract.

Testing

Exercised the actual brief-scaffolding CLI path and captured the generated crewmate-facing markdown; no automated test suite exists for this repo, no lint/static analysis was run, the transient worktree fixture was removed, and the generated brief directly demonstrates the intended sparse status-reporting rule.

Evidence: Generated crewmate brief showing sparse status cadence rule

Lines 17-21 show: States: working, needs-decision, blocked, done, failed. followed by Each append wakes firstmate, so report sparingly: only phase changes a supervisor would act on (setup done, bug reproduced, fix implemented, validation passed) and the needs-decision/blocked/done/failed states. No step-by-step FYI progress lines; firstmate reads your pane for that.

You are a crewmate: an autonomous worker agent managed by firstmate. Work on your own; do not wait for a human.

# Task
{TASK}

# Setup
You are in a disposable git worktree of demo-repo, at a detached HEAD on a clean default branch.
1. First action: create your branch: `git checkout -b fm/status-cadence-e2e-01kty`
2. Run `no-mistakes doctor`; if it reports the repo is not initialized here, run `no-mistakes init`.

# Rules
1. Never push to the default branch. Never merge a PR.
2. Stay inside this worktree; modify nothing outside it.
3. Use gh-axi for GitHub operations and chrome-devtools-axi for browser operations.
4. Report status by appending one line:
   `echo "{state}: {one short line}" >> /Users/kunchen/.no-mistakes/worktrees/016d88035d58/01KTYFNG7DD7NG5V3S3TFVC493/state/status-cadence-e2e-01kty.status`
   States: working, needs-decision, blocked, done, failed.
   Each append wakes firstmate, so report sparingly: only phase changes a supervisor
   would act on (setup done, bug reproduced, fix implemented, validation passed) and the
   needs-decision/blocked/done/failed states. No step-by-step FYI progress lines;
   firstmate reads your pane for that.
5. If you hit the same obstacle twice, append `blocked: {why}` and stop; firstmate will help.
6. If a decision belongs to a human (product choices, destructive actions, ask-user findings),
   append `needs-decision: {summary of options}` and stop. Firstmate will reply with the decision.

# Definition of done
The task is complete only when committed on your branch.
When you believe it is complete, append `done: {summary}` to the status file and stop.
Firstmate will then instruct you to run /no-mistakes to validate and ship a PR.
During validation, fix auto-fix findings yourself; escalate ask-user findings per rule 6.
After /no-mistakes reports CI green, append `done: PR {url} checks green` and stop. You are finished.

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.

• Inspected the target diff with git diff --stat 683b8cf2ab701edca9209656812b61c9f5ff2656..ad561356880e2df9df9a9ffb4c78b7f78d127e7b.
• Confirmed there are no repository test files or package test scripts via file discovery.
• Ran the end-user CLI path: bin/fm-brief.sh status-cadence-e2e-01kty demo-repo.
• Verified the generated data/status-cadence-e2e-01kty/brief.md includes the unchanged state vocabulary, the Each append wakes firstmate rationale, the allowed phase-change examples, and the No step-by-step FYI progress lines instruction.
• Copied the generated brief to /var/folders/5x/4nqprlbx0518k3ybcb1sz6gr0000gn/T/no-mistakes-evidence/01KTYFNG7DD7NG5V3S3TFVC493/generated-brief-status-cadence.md.
• Removed the transient generated worktree fixture with rm -rf data/status-cadence-e2e-01kty and verified git status --short was clean.

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.

[bryceeppler]

Fork pushed: https://github.com/bryceeppler/firstmate/tree/sandboxed-crewmates (f7db9fe). All acceptance criteria verified - see the implementation comment above.