test(footnotes): cover footnoteWarnings import plumbing + doc fixes (#169 second review)

Follow-up to the merged #166/#169. Addresses the second review pass (comment
1227):

- footnoteWarnings plumbing: extract a single `footnoteWarningsField(markdown)`
  helper (footnote-analyze) and use it at all three call sites (create_page,
  update_page, import_page_markdown) so the field is attached identically.
- New unit test footnote-warnings-import.test.mjs pins the contract that was
  uncovered: the field is present on problems / omitted on clean input, and the
  IMPORT path analyzes the BODY after the docmost:meta / docmost:comments blocks
  (a footnote-like token inside those JSON blocks must NOT warn; a real body
  marker must). Tested via the same pure composition the importer uses
  (footnoteWarningsField(parseDocmostMarkdown(full).body)) — no collab socket
  needed; a regression that analyzed fullMarkdown or skipped the body split would
  now go red.
- footnote.marked.ts: correct the stale module header — it claimed "only
  definitions that have a matching reference are emitted", which was never true
  (orphan defs are emitted; the editor sync plugin reconciles). Now describes
  first-wins + reuse + sync reconciliation.
- derive-id golden test: rename the describe from "(cross-package drift guard)"
  to "(deterministic-scheme pin)" — there is no second package to drift against.

editor-ext 129, MCP 304 (+3), client+server tsc clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/mcp/build/client.js

@@ -9,7 +9,7 @@ import WebSocket from "ws";
 import { convertProseMirrorToMarkdown } from "./lib/markdown-converter.js";
 import { updatePageContentRealtime, replacePageContent, markdownToProseMirror, mutatePageContent, buildCollabWsUrl, assertYjsEncodable, } from "./lib/collaboration.js";
 import { docmostExtensions } from "./lib/docmost-schema.js";
-import { analyzeFootnotes } from "./lib/footnote-analyze.js";
+import { footnoteWarningsField } from "./lib/footnote-analyze.js";
 import { buildPageTree } from "./lib/tree.js";
 import { serializeDocmostMarkdown, parseDocmostMarkdown, } from "./lib/markdown-document.js";
 import { replaceNodeById, deleteNodeById, insertNodeRelative, buildOutline, getNodeByRef, readTable, insertTableRow, deleteTableRow, updateTableCell, } from "./lib/node-ops.js";
@@ -820,8 +820,7 @@ export class DocmostClient {
         const page = await this.getPage(newPageId);
         // Surface non-fatal footnote problems (dangling refs, empty/duplicate
         // definitions, markers in tables) so the agent can fix its markup (#166).
-        const { warnings } = analyzeFootnotes(content);
-        return warnings.length > 0 ? { ...page, footnoteWarnings: warnings } : page;
+        return { ...page, ...footnoteWarningsField(content) };
     }
     /**
      * Update a page's content from markdown and optionally its title.
@@ -851,7 +850,6 @@ export class DocmostClient {
             }
             throw new Error(`Failed to update page content: ${error.message}`);
         }
-        const { warnings } = analyzeFootnotes(content);
         return {
             success: true,
             modified: true,
@@ -859,7 +857,7 @@ export class DocmostClient {
             pageId: pageId,
             verify: mutation.verify,
             // Non-fatal footnote diagnostics (#166); omitted when there are none.
-            ...(warnings.length > 0 ? { footnoteWarnings: warnings } : {}),
+            ...footnoteWarningsField(content),
         };
     }
     /**
@@ -1129,11 +1127,11 @@ export class DocmostClient {
         if (meta?.pageId && meta.pageId !== pageId) {
             result.warning = `File was exported from page ${meta.pageId} but is being imported into ${pageId}.`;
         }
-        // Non-fatal footnote diagnostics (#166), analyzed on the body (definitions
-        // and references live there, not in the front-matter/comments sections).
-        const { warnings } = analyzeFootnotes(body);
-        if (warnings.length > 0)
-            result.footnoteWarnings = warnings;
+        // Non-fatal footnote diagnostics (#166), analyzed on the BODY (the part after
+        // the docmost:meta / docmost:comments blocks) — so a `[^x]`-like token inside
+        // those JSON blocks never produces a false warning, while real markers in the
+        // body do. `body` comes from parseDocmostMarkdown(fullMarkdown) above.
+        Object.assign(result, footnoteWarningsField(body));
         return result;
     }
     /**