fix(pull-requests): relax pull_request_review_write required fields for resolve_thread

[ningyixi]

Summary

Relax pull_request_review_write advertised inputSchema.required so resolve_thread / unresolve_thread can be called with only threadId, matching the tool description and granular tools.

Why

Fixes #3501

Schema-validating MCP clients (VS Code MCP, Claude Desktop, Cursor, etc.) reject documented resolve_thread / unresolve_thread calls because the root schema required owner, repo, and pullNumber for every method, even though those methods only use threadId.

What changed

• Root Required for pull_request_review_write is now ["method"] (same pattern as discussion_comment_write).
• Document that owner / repo / pullNumber are required for create / submit_pending / delete_pending.
• normalizePullRequestReviewWriteArguments validates per method: threadId for resolve/unresolve; owner+repo+pullNumber for create/submit/delete.
• Updated toolsnaps, README / feature-flags docs, and regression tests.

MCP impact

• Tool schema or behavior changed
  • Advertised required fields for pull_request_review_write no longer include unused repo coordinates for thread resolve/unresolve.
  • Missing repo coordinates on create/submit/delete now fail early with a clear normalize error instead of an empty GraphQL lookup.

Prompts tested (tool changes only)

• Resolve a review thread with pull_request_review_write using only method: resolve_thread and threadId: PRRT_...
• Create a pending review without owner/repo and confirm the call fails with owner, repo, and pullNumber are required for create method

Security / limits

• No security or limits impact

Tool renaming

• I am not renaming tools as part of this PR

Lint & tests

• Linted locally with ./script/lint (skipped; focused package tests only)
• Tested locally with related go test ./pkg/github/ -run 'PullRequest|ReviewWrite|ResolveReview|TestPullRequestReviewWriteResolveThreadSchema|...' (pass)

Docs

• Updated (README / docs / examples via ./script/generate-docs)