chore: remove pre-pivot dead code + finish Scribe rebrand (#599 t1-3)

- Header wordmark Fabled -> Scribe; fable:calendar-changed event ->
  scribe:calendar-changed; SettingsView CSS comment.
- Drop dead Project.auto_summary + summary_updated_at columns (migration
  0063) -- the Ollama-era summarizer is gone; model + 2 frontend types +
  projects test updated.
- Remove pivot vestiges: diagnostics _curator_busy()/curator_busy
  heartbeat field, tz BRIEFING_DAY_START_HOUR/user_briefing_date dead
  aliases, the ignored 'model' param on get_embedding (+ its test).

ruff src/ clean; CI is the gate. Part of scribe plan #599.

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

alembic/versions/0063_drop_project_auto_summary.py

@@ -0,0 +1,34 @@
+"""drop dead Project.auto_summary columns
+
+Revision ID: 0063
+Revises: 0062
+Create Date: 2026-06-03
+
+auto_summary + summary_updated_at were written by generate_project_summary
+(Ollama), removed in the MCP pivot. Nothing has populated them since; the
+field was stale-or-NULL. Drop the columns.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "0063"
+down_revision = "0062"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.drop_column("projects", "auto_summary")
+    op.drop_column("projects", "summary_updated_at")
+
+
+def downgrade() -> None:
+    op.add_column(
+        "projects",
+        sa.Column("summary_updated_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.add_column(
+        "projects",
+        sa.Column("auto_summary", sa.Text(), nullable=True),
+    )