Replace passage buttons with a full-page visual editor - #13

Readers currently have to choose a paragraph using repeated buttons and cannot edit tables or propose larger changes. Replace that flow with a quiet “Edit this page” link and a dedicated Milkdown editor for the complete page body. Readers can edit sections, lists, links, inline code, and tables, review highlighted changes, recover local drafts, and submit without an account.

The existing Cloudflare/D1/GitHub App pipeline now accepts full-page proposals. The server keeps frontmatter immutable and validates Markdown independently. Unchanged source blocks are preserved verbatim; changed blocks may be normalized. A stale draft branches from its original verified commit so GitHub exposes conflicts instead of overwriting newer content. Legacy passage submissions remain supported.

Milkdown 7.22.1 is pinned. Narrow adapters handle empty table-cell placeholders and provide accessible keyboard toolbar controls. One existing <parameter> placeholder is formatted as inline code so it no longer parses as HTML. Editor assets are loaded only on editing routes; release builds omit those routes and frozen archives remain unchanged. The editor's main lazy chunk is approximately 173 KB gzip.

Validation:

• All 98 documentation pages pass actual Milkdown import/export, byte-identical no-op saves, and edited-content preservation in Chromium.
• Five browser scenarios pass: complete corpus; multi-section editing/draft recovery/review/failure/retry/receipt; mobile table editing; problem reporting; keyboard toolbar operation. Manual-version context is preserved. Submission and Turnstile responses are mocked in browser tests.
• 26 service/source/security/delivery tests pass, including stale full-page branching and duplicate recovery.
• Enabled, disabled, and release-mode builds pass; Worker dry-run and archive-preservation test pass.
• Desktop 1440×1000 and mobile 390×844 screenshots were inspected. No unexpected runtime errors in the tested desktop flow.

Deployment: the compatible Worker update is deployed separately before this UI is merged. The public interface changes after merge and Pages deployment. A live full-page submission through production Turnstile remains a post-merge launch check. Safari, native mobile keyboards, and unaided-reader usability are not yet verified.