feat(github-app): new maintainer @gittensory commands

[JSONbored]

Parent roadmap: #525
Parent phase: #528

Background

Maintainer intelligence (burden forecast, intake health, outcome patterns, noise report) is already computed but not reachable from the PR thread where maintainers work.

Goal

Add new maintainer @gittensory commands that render existing builders into the thread.

Current Behavior

The maintainer catalog (src/github/commands.ts:22) has queue-summary/confirmed-miners/review-now/needs-author/duplicate-clusters only.

Desired Behavior

• Add burden-forecast (wraps buildBurdenForecast engine.ts:2954), intake-health (buildContributorIntakeHealth :2227), outcome-patterns (buildRepoOutcomePatterns :1904), noise-report (buildMaintainerNoiseReport reward-risk.ts:386).
• Authorization is automatic via the existing default [maintainer, collaborator] policy.

Implementation Requirements

• Add to MAINTAINER_QUEUE_DIGEST_COMMAND_CATALOG; thin renderers over the builders.

Public/Private Output Boundaries

• All output through the public-safe filter; no reward/trust internals.

Acceptance Criteria

• Each command renders its builder's output, gated maintainer-only.

Testing Requirements

• npm run test:ci, 97%+ coverage. Authorization + render tests per command.