feat(bugs): add --format json to bugs show and bugs close

[sachiniyer]

Summary

Triage agents repeatedly grep stdout for fields that are already in the JSON payload — bug metadata (file path, security flag, blame, summary) for show, and the resulting BugReview for close. Only bugs list accepted --format json; show and close forced text-parsing.

Add --format <table|json> (default table) to both subcommands:

• bugs show <id> --format json — emits the full Bug payload (id, title, summary, filePath, introducedIn, review, linkedIssues, …)
• bugs close <id> --state <s> --format json — emits the resulting BugReview, suppressing the human-friendly "✓ Bug closed as: …" banner so stdout is pure JSON

is_silent extended to suppress auto-update notices on the new JSON paths, matching how bugs list --format json already works.

The table-view body of Show is unchanged; extracted into a render_bug_show helper so the handler match arm just dispatches on format.

Testing

Automated, run locally and passing:

• cargo test — full suite green. New clap-parse tests in src/lib.rs:
  • silent_when_bugs_show_json — bugs show … --format json triggers the silent-output path
  • silent_when_bugs_close_json — same for close
  • Existing not_silent_for_bugs_show / not_silent_for_bugs_close still pass (default format is table)
• cargo clippy -- -D warnings — clean
• cargo fmt --check — clean
• cargo xtask check — clean (HELP.md regenerated for the two new flags)

Manual end-to-end against live API:

• bugs show bug_5d237de8-… --format json → valid JSON, all expected fields present:

  keys: ['createdAt', 'filePath', 'id', 'introducedIn', 'isSecurityVulnerability',
         'linkedIssues', 'repoId', 'summary', 'title']
  

• bugs show bug_5d237de8-… (default) → unchanged: ID/Title/File/Created/Security/Introduced/Issue rows + markdown summary
• bugs close bug_e79362bd-… --state dismissed --dismissal-reason not-a-bug --format json (idempotent re-close on an already-dismissed bug) → emits the BugReview JSON only, no ✓ Bug closed as: banner. head -1 of stdout is just {.
• bugs show bug_does_not_exist --format json → Error: Failed to fetch bug details (still propagates errors via stderr; stdout stays empty)

⚠️ Pre-existing bug found while testing (not part of this PR, flagged for follow-up):
bugs close without --notes overwrites any existing review.notes with null — the API client sends notes: None which the backend treats as "set to null" rather than "leave unchanged". Caught when re-closing an already-dismissed bug for this PR's smoke test; the original notes were restored manually. Not introduced by this PR but tagged for follow-up.

🤖 Generated with Claude Code

[cubic-dev-ai]

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