fix(engine): redact blocklisted terms in chat-grounding tool_result events

[joaovictor91123]

Summary

• Apply the same PUBLIC_FIELD_BLOCKLIST redaction used for assistant text chunks to string tool_result content in chat-grounding.
• Cover the new path in the vitest suite (codecov) and the mirrored engine node:test suite; non-string tool payloads still pass through unchanged.

Closes #8869

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• 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 a currently open issue this PR resolves (e.g. Closes #123) — a linked open issue is required for every contributor PR.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; codecov/patch requires ≥99% coverage of the lines AND branches you changed (aim for 100% on your diff so CI variance does not fail near the threshold). Global coverage is a non-blocking trend with a loose 90% backstop, not the gate.
• 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

If any required check was skipped, explain why:

• Full suite not re-run locally (Node 24 vs engines Node 22). Diff is one redaction call site plus unit coverage for the string redaction and non-string passthrough branches; CI is source of truth.

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 a UI Evidence section below with JPG/JPEG or PNG screenshots arranged as organized, captioned, clickable thumbnails. SVG screenshots are not used as review evidence. Review-only screenshots or recordings are not committed to the repository.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

UI Evidence

N/A — no visible UI changes.

Notes

• Closes a privacy leak where MCP tool output could forward blocklisted fields into the public chat-grounding stream.

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[joaovictor91123]

Closing to re-open on latest main. CI failed on the same unrelated flake in miner-worktree-allocator-collisions (distinct-path acquire race). chat-grounding-engine.test.ts (39 tests) passed green; one-shot policy forbids a follow-up push.