feat: add evidence-driven bug report skill

[time-attack]

Summary

• Add /bug-report, an evidence-driven workflow that reconstructs user actions, captures scoped diagnostics, attempts safe reproduction, and separates confirmed facts from hypotheses.
• Produce maintainer-ready issue and PR-body drafts with executable reproduction and verification guidance.
• Require explicit approval before remote publication and keep the skill report-only; fixes route to /investigate.
• Add exact-byte redaction gates for reports, PR bodies, and each evidence artifact, plus cleanup requirements for raw temporary diagnostics.
• Register the skill in GStack routing, documentation, generated catalogs, and the coverage matrix.

Test Coverage

• 352 focused tests passed across the bug-report invariants, redaction resolver, coverage matrix, and structural skill floor.
• All-host generated skill output is fresh.
• The workflow was manually exercised against historical GBrain issue Restructure setup phases to improve failure handling and fix bugs #1883: GBrain 0.42.31.0 reproduced the numeric-title lint crash, while current GBrain scanned all 4/4 fixture pages successfully.

Pre-Landing Review

Privacy review findings were addressed before push:

• Every persisted artifact is now an independent redaction sink.
• Scanned bytes are retained until the corresponding write succeeds.
• Raw diagnostic directories require finally-style cleanup or explicit retention approval.

Design Review

No frontend files changed.

Eval Results

No paid model eval was run. Deterministic skill and resolver tests pass, and the workflow received a real historical regression exercise in an isolated environment.

Plan Completion

No plan file detected.

TODOS

No TODO items completed in this PR.

Test plan

• Bug-report skill invariants
• Redaction resolver lifecycle tests
• Skill coverage registry and structural floor
• All-host generation freshness
• Historical GBrain regression reproduction

No version, package metadata, or changelog bump is included; this is the raw skill contribution requested by the contributor.

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[capy-ai]

Thank you for this, @time-attack, and for the work that went into it. We reviewed it against current main and decided not to take it: /investigate and /qa-only already cover diagnosis and reporting; the redaction-before-publish gate is the reusable idea. Closing it with thanks; if the underlying problem still bites you, an issue describing it is very welcome.