Project-aware assist, link suggestions, project-scoped RAG, semantic search tool, SSE race fix

- Writing assistant: inject project notes as context (definition-tagged first), wikilink suggestions
- Link suggestions: server-side endpoint finds unlinked term occurrences, NoteEditorView sidebar panel
- Project-scoped RAG: ChatView ProjectSelector filters semantic+keyword search to selected project
- Semantic search tool: LLM search_notes upgraded to hybrid semantic (0.40 threshold) + keyword merge
- SSE race condition fix: drain remaining events after stream loop exits in chat.py and notes.py
- RAG_AUTO_SNIPPET raised 800→4000; sidebar include uses full note body; MAX_BODY_CHARS 8000→24000
- Enter-to-submit on writing assistant instruction textareas (note and task editors)
- DiffView: equal-line collapsing with 3-line context around changes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/models/note_version.py

@@ -1,6 +1,6 @@
 from datetime import datetime, timezone
 
-from sqlalchemy import DateTime, ForeignKey, Integer, Text
+from sqlalchemy import ARRAY, DateTime, ForeignKey, Integer, Text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from fabledassistant.models import Base
@@ -14,6 +14,7 @@ class NoteVersion(Base):
     user_id: Mapped[int] = mapped_column(Integer, ForeignKey("users.id", ondelete="CASCADE"))
     body: Mapped[str] = mapped_column(Text)
     title: Mapped[str] = mapped_column(Text, default="")
+    tags: Mapped[list[str]] = mapped_column(ARRAY(Text), default=list)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
     )
@@ -24,6 +25,7 @@ class NoteVersion(Base):
             "note_id": self.note_id,
             "user_id": self.user_id,
             "title": self.title,
+            "tags": self.tags or [],
             "created_at": self.created_at.isoformat(),
         }
         if include_body: