fix(brief): pin decision key placement in generated briefs

[eduardstan]

Problem

bin/fm-classify-lib.sh requires [key=<slug>] between the status verb and the colon, but the generated scaffolds did not say so. Workers therefore wrote keys at the end of status lines, and the key never registered.

Changes

• Clarified parser-accepted key placement in ship, scout, and secondmate briefs.
• Added regression coverage for the incident line and correctly placed keys.
• Kept the parser strict because trailing bracketed prose is ambiguous.

Validation: tests/fm-brief.test.sh, focused classifier coverage, tests/fm-send-resolve-key.test.sh, and bin/fm-lint.sh pass.

[eduardstan]

The required PR must be raised via no-mistakes check fails here because this branch was pushed directly rather than through that pipeline. I will re-raise the same change through the required path and close this one; no review time is needed on it in the meantime.

[eduardstan]

Superseded by #2168, which carries the same change raised through the required no-mistakes pipeline.