fix(signals): public-safety boundary does not redact /root/ local paths

[kiannidev]

Summary

The signals public/private boundary treats /Users/, /home/, and /tmp/ (and Windows …\Users\…) as local filesystem paths that must never reach a public GitHub surface, but it does not recognize /root/ — the root user's home directory. A contributor who runs local branch analysis from a /root/... working tree (common in containers, CI, and devcontainers) can leak that absolute local path onto public surfaces.

The project already considers /root/ a local path elsewhere: src/services/miner-dashboard-recommendations.ts redacts it.

// src/services/miner-dashboard-recommendations.ts
const LOCAL_PATH = /(?:\/(?:Users|home|root|tmp|var)\/[^\s,;:)]+|[A-Za-z]:\\Users\\[^\s,;:)]+)/g;

So the intent is established; the canonical boundary primitive and its sibling have simply drifted.

Affected code (this issue's scope)

• src/signals/redaction.ts — PUBLIC_UNSAFE_PATTERN, the canonical isPublicSafeText boundary that governs PR/issue comments, check annotations, notifications, badge, and extension payloads. Its alternation lists /Users/|/home/|/tmp/ but omits /root/.
• src/signals/local-branch.ts — safeRepoPath, which redacts changed file paths rendered into the public PR packet (Changed Paths). Same ^(/Users/|/home/|/tmp/|…) denylist, also missing /root/. This is the most likely place a /root/... path appears, since it formats real changed-file paths.

Repro

import { isPublicSafeText } from "./src/signals/redaction";
isPublicSafeText("/root/project/src/index.ts"); // returns true (should be false)

A changed file at /root/work/src/cache.ts is rendered verbatim into the public PR packet's Changed Paths instead of [local path hidden].

Proposed fix

Add /root/ to both denylists so the signals boundary treats the root home directory like the other local paths, matching the existing miner-dashboard-recommendations.ts behavior. Add tests for the new case in test/unit/redaction.test.ts and test/unit/local-branch.test.ts.

Scope

Narrow, behavior-preserving for every existing input (only adds /root/ detection). Other surfaces that keep their own context-specific path denylists (control-panel-roles.ts, weekly-value-report.ts, db/repositories.ts, agent-action-explanation-card.ts, focus-manifest.ts) can be aligned in a follow-up; this issue is scoped to the canonical signals boundary primitive and the changed-file-path redactor.