feat(mcp): add safe planning elicitation

[bitloi]

Summary

• Closes feat(mcp): add non-sensitive elicitation for planning choices #275.
• Adds an allowlisted MCP form elicitation request for gittensory_agent_plan_next_work when a client supports form elicitation and planner context is missing.
• Applies only safe planning choices (repoFullName, contribution lane, time horizon, risk appetite, cleanup-first) and keeps explicit tool inputs authoritative.
• Returns deterministic audit metadata plus sanitized accepted choices so MCP clients can see whether elicitation was supported, requested, and accepted.

Scope

• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked an issue, or this is small enough that the summary explains why an issue is not needed.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; global coverage stays at or above 97% for lines, statements, functions, and branches (aim for 98%+ branch coverage locally so CI variance does not fail near the threshold)
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

Additional focused checks:

• npm run test -- test/unit/mcp-planning-elicitation.test.ts
• npm run typecheck
• npm run test:ci

If any required check was skipped, explain why:

• None.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests.
• API/OpenAPI/MCP behavior is updated and tested where needed.
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks.
• Visible UI changes include screenshots or a short recording.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

Notes

• No UI, migration, deploy, dependency, docs, or changelog changes.
• MCP clients without form elicitation continue to run gittensory_agent_plan_next_work with defaults and explicit inputs.
• Sensitive-field attempts are blocked by request validation and accepted elicitation content is filtered through the planning-choice allowlist.

[JSONbored]

@bitloi this looks mergeable.

A few notes:

• The elicitation surface is scoped to planning and does not try to make Dosu or the MCP path decisive.
• The branch is locally merge-clean against current main.
• No code changes requested.

Validation expected:

• Keep the current green CI run after any required branch update.