fix(bin): refuse task id reuse when data directory exists

[BohnBawerick]

Intent

Refuse task id reuse in fm-brief.sh when a data/ directory already exists to protect retained reports and prevent stale task instruction collisions

What Changed

• Added a validation in bin/fm-brief.sh that requires a task ID and refuses brief creation if $DATA/<id> already exists, reporting the existing path contents and exiting with an error.
• Added tests in tests/fm-brief.test.sh verifying task ID reuse refusal across existing files and directories, and updated test teardowns to remove full task data directories.
• Added a retry loop in tests/fm-calm-pi-extension.test.sh when capturing tmux pane contents.

Risk Assessment

✅ Low: The change cleanly refuses task ID reuse when a task data directory already exists, protecting retained artifacts with clear error reporting and thorough test coverage.

Testing

Executed targeted unit tests in tests/fm-brief.test.sh and performed end-to-end verification of bin/fm-brief.sh demonstrating refusal on existing data/<id> directories/files and report preservation, with evidence recorded in /tmp/no-mistakes-evidence/01M0AZQVAQWN146YANWJVWCVBY/task-id-reuse-cli-transcript.txt.

Evidence: CLI transcript demonstrating task ID reuse refusal and retained report preservation

Source: CLI transcript demonstrating task ID reuse refusal and retained report preservation

=== Scenario 1: Refusing task ID reuse with existing retained report ===
[Attempting to scaffold task-101]
error: task id 'task-101' already exists at /tmp/tmp.LMGXHKvA1H/demo-home/data/task-101 (contains: report.md); choose a distinct task id (e.g. 'task-101-2' or mint a new one) to preserve retained history and avoid collisions
[Command exited non-zero as expected]
[Checking preserved report.md content:]
Original report from previous run
[Checking brief.md does not exist:]
brief.md is absent (protected)

=== Scenario 2: Refusing task ID reuse with multiple artifacts ===
[Attempting to scaffold task-102 with --scout]
error: task id 'task-102' already exists at /tmp/tmp.LMGXHKvA1H/demo-home/data/task-102 (contains: brief.md, report.md); choose a distinct task id (e.g. 'task-102-2' or mint a new one) to preserve retained history and avoid collisions
[Command exited non-zero as expected]

=== Scenario 3: Refusing task ID reuse with empty directory ===
[Attempting to scaffold task-103 with --mode direct-PR]
error: task id 'task-103' already exists at /tmp/tmp.LMGXHKvA1H/demo-home/data/task-103 (empty directory); choose a distinct task id (e.g. 'task-103-2' or mint a new one) to preserve retained history and avoid collisions
[Command exited non-zero as expected]

=== Scenario 4: Refusing task ID reuse with existing file ===
[Attempting to scaffold task-104 with --mode local-only]
error: task id 'task-104' already exists at /tmp/tmp.LMGXHKvA1H/demo-home/data/task-104 (existing file); choose a distinct task id (e.g. 'task-104-2' or mint a new one) to preserve retained history and avoid collisions
[Command exited non-zero as expected]

=== Scenario 5: Successful scaffolding with fresh/unused task ID ===
[Attempting to scaffold task-105 with --mode no-mistakes]
scaffolded: /tmp/tmp.LMGXHKvA1H/demo-home/data/task-105/brief.md (ship, mode=no-mistakes; replace {TASK})
[Command exited 0 as expected]
[Checking brief.md was created:]
brief.md successfully generated

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-brief.test.sh
• bin/fm-brief.sh task ID reuse refusal verification across existing retained report, multi-artifact directory, empty directory, existing file, and fresh ID creation

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.

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