wire decisions, tickets, markdown viewer, and graph extensions

Four stub extensions now contribute real tabs with views:

- Decisions panel (sidebar, priority -20): lists confirmed D-records
  from pql decisions list with ID, title, and domain.
- Tickets panel (sidebar, priority -10): lists tickets with status
  dot color-coded by state (done=green, in_progress=blue,
  cancelled=red).
- Markdown viewer (context, priority -100): shows raw content of
  the active .md file, listens for editor.buffer_activated events.
- Graph view (context, priority -80): lists files with inbound and
  outbound link counts from pql search --connections.

All four fetch data via the daemon's pql.exec IPC surface.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -53,6 +53,18 @@ heading, and (b) bumping `project.yaml` `version:` in the same commit.
   weights. Replaces hand-painted CustomPaint icons in sidebar and
   context panel icon rails.
 
+- Decisions panel in sidebar — lists confirmed D-records from
+  `pql decisions list` with ID and title (T-037).
+
+- Tickets panel in sidebar — lists tickets from `pql ticket list`
+  with status dot color-coded by state (T-037).
+
+- Markdown viewer in context panel — shows raw content of the
+  active .md file, auto-updating on buffer switch (T-038).
+
+- Graph view in context panel — lists files with inbound/outbound
+  link counts from `pql search --connections` (T-039).
+
 ### Changed
 
 - Workspace renders Claude as the always-visible primary surface