feat(superdoc): deprecate ProseMirror internals and editor commands (SD-2434) (#2674)

* feat(superdoc): deprecate ProseMirror internals and editor commands in public API (SD-2434)

Add soft deprecation layer to steer consumers toward the Document API
(editor.doc) ahead of the planned ProseMirror removal:

- Add @deprecated JSDoc to editor.state, editor.view, editor.schema,
  editor.commands, editor.chain(), editor.can(), editor.dispatch()
- Add @deprecated to ProseMirror and command type re-exports from both
  super-editor and superdoc packages
- Wrap editor instances at consumer boundary (onEditorCreate callback)
  with a Proxy that emits one-time runtime deprecation warnings
- Internal code paths are unaffected — Proxy only applies at the
  broadcastEditorCreate/broadcastEditorBeforeCreate boundary

* docs: add deprecation notices for ProseMirror internals and editor commands (SD-2254)

- Update ProseMirror migration guide with deprecation warnings and
  Document API examples as the recommended alternative
- Add deprecation banner to editor commands section in methods.mdx
- Update AGENTS.md to recommend Document API for programmatic access
  instead of editor.commands

* docs: hide extensions section from nav and add gap analysis (SD-2254)

- Remove Extensions group from docs.json navigation
- Add hidden: true frontmatter to all 57 extension pages (still
  accessible via direct URL for existing users)
- Add EXTENSION-TO-DOCAPI-GAPS.md mapping all 66 extension commands
  that lack Document API equivalents, categorized by priority

* fix(superdoc): bind proxy reads to target for private field compatibility (SD-2434)

Use Reflect.get with target instead of receiver so Editor getters that
access private fields (#commandService, #documentApi, etc.) work
correctly through the deprecation proxy. Also bind returned methods to
the target instance.

* fix(superdoc): cache bound functions in proxy and add unit tests (SD-2434)

- Cache bound functions in a WeakMap so repeated method access through
  the deprecation proxy returns the same reference (preserves identity)
- Add 18 unit tests covering warnOnce deduplication, deprecated/
  non-deprecated property access, function binding, guard clauses,
  double-wrap prevention, and unwrapEditor round-tripping

* docs: restructure navigation for developer experience (SD-2254)

Reorganize docs sidebar to match how developers think:

- Rename "Modules" → "Features" and move theming/fonts there
- Promote Document API to top-level section (was nested under
  Document Engine)
- Promote AI Agents to top-level (was nested under Document Engine)
- Dissolve "Document Engine" — SDKs and CLI become "SDKs & Tools"
- Rename "Core" → "API Reference" and move to bottom
- Add MCP Server to AI Agents nav (was only reachable via subpage)
- Remove fonts/theming from Getting Started (now under Features)
- Keep Resources as standalone section

No file moves — navigation-only restructure. URLs unchanged.

* Revert "docs: restructure navigation for developer experience (SD-2254)"

This reverts commit a969086.

* chore: remove gap analysis doc from repo (SD-2434)

* docs: add commands-to-Document API migration guide (SD-2254)

- Write migration guide mapping editor.commands patterns to editor.doc
  equivalents (formatting, comments, track changes, tables, lists, etc.)
- Add guide to docs navigation under Migration section
- Update deprecation runtime warning URL to point to migration guide
- Tighten prosemirror migration guide voice to match brand guidelines

* docs: remove emojis from migration guide code comments (SD-2254)

Replace emoji markers in code examples with plain text labels to
align with brand voice guidelines.

Author: caio-pizzol

apps/docs/core/supereditor/methods.mdx

@@ -157,69 +157,6 @@
               "modules/whiteboard"
             ]
           },
-          {
-            "group": "Extensions",
-            "pages": [
-              "extensions/overview",
-              {
-                "group": "All",
-                "pages": [
-                  "extensions/block-node",
-                  "extensions/bold",
-                  "extensions/bookmarks",
-                  "extensions/bullet-list",
-                  "extensions/color",
-                  "extensions/content-block",
-                  "extensions/custom-selection",
-                  "extensions/document",
-                  "extensions/document-index",
-                  "extensions/dropcursor",
-                  "extensions/font-family",
-                  "extensions/font-size",
-                  "extensions/footnote",
-                  "extensions/format-commands",
-                  "extensions/gapcursor",
-                  "extensions/heading",
-                  "extensions/highlight",
-                  "extensions/history",
-                  "extensions/image",
-                  "extensions/italic",
-                  "extensions/line-break",
-                  "extensions/line-height",
-                  "extensions/link",
-                  "extensions/linked-styles",
-                  "extensions/list-item",
-                  "extensions/mention",
-                  "extensions/noderesizer",
-                  "extensions/ordered-list",
-                  "extensions/page-number",
-                  "extensions/paragraph",
-                  "extensions/permission-ranges",
-                  "extensions/placeholder",
-                  "extensions/popover-plugin",
-                  "extensions/run-item",
-                  "extensions/search",
-                  "extensions/shape-container",
-                  "extensions/shape-textbox",
-                  "extensions/context-menu",
-                  "extensions/strike",
-                  "extensions/structured-content",
-                  "extensions/tab",
-                  "extensions/table",
-                  "extensions/table-cell",
-                  "extensions/table-header",
-                  "extensions/table-of-contents",
-                  "extensions/table-row",
-                  "extensions/text-align",
-                  "extensions/text-indent",
-                  "extensions/text-style",
-                  "extensions/text-transform",
-                  "extensions/track-changes",
-                  "extensions/underline"
-                ]
-              }
-            ]
-          },
           {
             "group": "Solutions",
             "pages": [
@@ -266,6 +203,7 @@
               {
                 "group": "Migration",
                 "pages": [
+                  "guides/migration/document-api",
                   "guides/migration/prosemirror",
                   "guides/migration/breaking-changes-v1",
                   "guides/migration/typescript-migration",