feat(coach): document chats live in the Coach view and history

Asking the Coach about a document opened a separate, half-finished chat panel
that never appeared in Coach history. The bespoke drawer is gone; a document
conversation now opens the real Coach view, appears in the Coach list with a
document badge and a "Chatting about: <title>" note, and is read back through
the same history rail as any other thread.

The prompt-injection fence is unchanged and stays server-side. A document turn
is still sent through the hardened fenced endpoint (no tools, no health
snapshot, grounded in the document text only); the coach tool route continues
to fetch with documentId null, so a document-scoped conversation can never be
continued through the tool loop even from a hostile client. Only the surface
moved into the Coach; the boundary did not.

The relaxed conversation-list and detail filters drop only the documentId
predicate — userId scoping is unchanged, so a document thread is still visible
only to its owner. CoachConversationDTO gains documentId + documentTitle
(server-derived, title/filename only); no schema change (documentId exists
since 0230). OpenAPI regenerated.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.28.50",
+  "version": "1.28.51",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "PolyForm-Noncommercial-1.0.0",
   "homepage": "https://healthlog.dev",