feat(editor-compatibility): implement T19-01 published-post schema compatibility (#550)

[edithatogo]

Summary

Implements Conductor track T19-01 (Published-post editor schema compatibility and crash containment) across all 5 phases (resolving #550, #555, #556, #557, #558, #559):

1. Reproduction contract & frozen fixtures (Phase 1 T19-01 Phase 1: Reproduction contract and failing tests #555):
   • Freezes 8 privacy-safe ProseMirror fixtures in fixtures/prosemirror/editor-compatibility/:
     • cover-control.json: paragraph-only control (0 tables, 0 tableHeader).
     • rich-pilot-control.json: rich published pilot reproduction (0 tables, rich blocks).
     • 6 scheduled essay fixtures (me-001 through me-006) containing exactly 11 tables and 41 tableHeader nodes across the Season 1 corpus.
2. Static capability analyzer & 5 independent facets (Phase 2 T19-01 Phase 2: Static compatibility analyzer #556):
   • PUBLIC_RENDER_PROFILE, PRIMARY_EDITOR_PROFILE (rejects tableHeader), and AUXILIARY_EDITOR_PROFILE (rejects rich blocks).
   • Generates deterministic 16-character schema fingerprints for drift detection.
   • Evaluates 5 independent facets without collapsing: public render, stored body round-trip, primary editor compatibility, auxiliary editor risk, and browser live verification.
3. Transport, CLI & receipt integration (Phase 3 T19-01 Phase 3: Transport and receipt integration #557):
   • Prepublish and inspect reporting extended with editorCompatibility.
   • New CLI command substack-publisher schema compatibility <file> [--normalize-tables] [--upstream-repro <dir>].
4. Disposable canary & operational contingencies (Phase 4 T19-01 Phase 4: Authenticated canary and contingencies #558):
   • normalizeTablesToAccessibleLists contingency converts tables to accessible labelled lists, resolving primary editor rejection while preserving text content.
   • runDisposableEditorCanary enforces isolated, no-email, no-publication invariants with cleanup receipts.
5. Upstream escalation package (Phase 5 T19-01 Phase 5: Upstream escalation and release evidence #559):
   • generateMinimalUpstreamReproductionPackage produces clean minimal synthetic reproduction package for Substack engineers.

Validation

• npm run ci -> Biome 0 errors
• npm run typecheck -> Clean, 0 errors
• npm run knip -> Clean, 0 issues
• node scripts/github-programme.mjs check -> 100% valid
• npm run verify:agent -> 125 test files / 988 passed

Governed by #550, #555, #556, #557, #558, #559.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-06T13:03:15.970102Z	b2082bb	PR opened

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[amazon-q-developer]

This PR introduces a new editor compatibility checking system for Substack's ProseMirror/Tiptap schema validation. The implementation includes analyzer logic, profile definitions, normalization utilities, canary testing infrastructure, and integration into the prepublish workflow. The code is well-structured with proper TypeScript typing and no merge-blocking defects identified. All logic appears correct, error handling is appropriate, and there are no security vulnerabilities detected.

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[codecov]

Codecov Report

❌ Patch coverage is 82.06897% with 26 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/editor-compatibility/contingencies.ts	72.50%	2 Missing and 9 partials ⚠️
src/editor-compatibility/analyzer.ts	83.63%	5 Missing and 4 partials ⚠️
src/editor-compatibility/canary.ts	82.35%	2 Missing and 4 partials ⚠️

📢 Thoughts on this report? Let us know!

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: b2082bbb92

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