feat: add verify-bug skill and suspected-bug friction to whiteboard

[markphelps]

Adds verify-bug to the development plugin and a suspected-bug friction type to whiteboard.

verify-bug

Decides whether claimed bugs are real. It never hunts for new bugs and never fixes code.

• Input: any claim — suspected-bug entries from a whiteboard map, pasted findings, review comments, or GitHub issues — normalized into one claim record (scenario, receipt, severity-if-true, verdict slot).
• Hearing: per claim, three isolated roles. A Prover builds the trigger path, a Skeptic hunts for what prevents it, and a Referee rules confirmed (reproduced), confirmed (static), refuted, or unclear. Falls back to sequential roles without subagents.
• Repro: when cheap, the Prover writes a failing test in a throwaway git worktree under .verify/, saves it as a patch, and removes the worktree. The working tree is never touched. Asks before anything beyond the repo's own test command.
• Output: a local .verify/<date>-<slug>.md report (excluded via .git/info/exclude), in-place verdicts for map entries, and draft GitHub replies posted only after explicit confirmation.
• Scale: dedupe by code path and trigger, rank by severity-if-true, verify the top 10 by default; nothing is silently dropped.
• Triggering: implicit only when the user asks whether a claim is real or points at suspected bugs.

The Prover/Skeptic/Referee structure is borrowed as an idea from existing adversarial bug-hunt skills; no text is copied.

whiteboard

• New suspected-bug friction type. Entries must name a concrete triggering scenario and start as verdict: unverified; whiteboard never investigates them.
• Handoff by wording only ("these suspected bugs could be verified"), so neither skill depends on the other.
• Refuted suspected bugs become gradable adversarial defense questions; unverified or unclear ones are asked but not graded.
• Refresh preserves existing verdicts.

Checks

Ran locally: npm run format:check, npm run validate, and npm run sync (mirror under skills/ included).