Establish canonical app structure vocabulary

[lastobelus]

Summary

• define App shell, App header, Pane layout, Left pane, Center pane, and Right pane as Markover’s canonical first-level structure
• apply those names across DOM, TypeScript, CSS, settings, private workspace state, tests, the glossary, and repository documentation
• add a self-contained ELI5 architecture document while preserving all pre-existing palette values

Delivery order

This naming-only PR lands before #195. The inherited UI tweaks will then be rebuilt on this vocabulary and audited against it.

Validation

• npm run build
• 78 focused structure, accessibility, durability, navigation, settings, workspace, and inbox tests
• ELI5 verifier
• git diff --check
• full local suite: 823/824 pass; the sole failure is an unrelated current-main concurrency-order assertion in remote-creation-journal.test, which passes when run alone

Boundary

This PR changes names and architecture boundaries, not visual choices. It preserves the existing base and Olive-light computed pane/header colors. It excludes Claude’s UI color, typography, spacing, selection-bridge, scrollbar, tuner, and window-geometry tweaks, which remain in #195.

[lastobelus]

Work intent

phase: completed
summary: "Landed the canonical first-level app structure vocabulary as the naming-only foundation for #195."
touch-points:
  - AGENTS.md
  - GLOSSARY.md
  - DECISIONS.md
  - doc/design/
  - doc/plans/
  - docs/developer/app-structure.md
  - docs/user/
  - src/index.html
  - src/renderer.ts
  - src/contracts.ts
  - src/ipc-contract.ts
  - src/navigation.ts
  - src/review-sessions.ts
  - src/settings.ts
  - src/workspace-state.ts
  - src/styles.css
  - focused structure, navigation, settings, workspace, and UI tests
done-when:
  - "The six approved first-level terms are canonical across glossary, docs, DOM, TypeScript, CSS, settings, private state, and tests."
  - "The app shell and app header have truthful DOM boundaries."
  - "The ELI5 structure document verifies as self-contained."
  - "Existing pre-UI computed palette values are preserved."
  - "Current-head CI and automated review are green and the PR is merged before #195."
excludes:
  - "Claude UI color, typography, spacing, selection, scrollbar, token-tuner, and window-geometry tweaks."
  - "Naming pane contents, dialogs, settings organization, overlays, or child components."
  - "Color consolidation or other new visual decisions."
  - "Compatibility aliases or migrations for unreleased pre-MVP private UI state."
blocked-by: []
may-block:
  - "#195"
branch: "t3code/canonical-app-structure"

[lastobelus]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

Reviewed commit: 2af09666e6

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".