Bind GitHub events to repository-local PR identity

[krasnoperov-coding-agent]

Problem

A merged PR that merely mentioned a tracked issue key could be treated as that issue's owning PR. PR numbers and branch names were also looked up globally before checking the repository, making cross-repository identity collisions unsafe.

Change

• Resolve PR numbers, branches, and issue keys atomically within the configured repository.
• Allow issue-key discovery to establish ownership only on pr_opened.
• Require all later review, check, synchronize, close, and merge events to match persisted PR or branch identity.
• Cover foreign terminal events and cross-repository PR, branch, and issue-key collisions at both resolver and handler levels.

[review-quill]

Verdict: ✅ Approve — The current head scopes PR, branch, and issue-key lookup to the selected project and restricts issue-key discovery to PR-open events; no actionable regression was found.