unify agent items into a flat file-based store, drop the marketplace

Replace the marketplace service dependency and the native/global/user
scope tiers with a single external directory ($OFFICER_ITEMS_DIR) holding
skills, tools, tasks, processes and extensions as plain files.

- tasks move from Postgres to TASK.md files (new file-backed task layer);
  task editing now works, which the DB path never supported
- skills/tools/processes collapse into one shared file router (single dir)
- remove the marketplace client (sync-marketplace/sync-version) and the
  boot-time sync; pi-bridge/pi-manager/sandbox point at the flat store
- drop the dead tasks + vestigial skills/tools/processes/extensions +
  item_chats tables (migration 0004)
- one-time migration script exports DB tasks and consolidates disk items

Migration verified: all 6 tasks round-trip through the runtime parser
identically to their DB rows (pipeline steps, triggers, script impls and
agentic bodies all intact).

NOTE: not yet functionally tested end-to-end — every item (each task mode,
tool, skill, extension) still needs to be run/exercised in the app before
this is trusted. To be done manually.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/databases/officer_db/migrations/meta/_journal.json

@@ -29,6 +29,13 @@
       "when": 1773040399200,
       "tag": "0003_perpetual_james_howlett",
       "breakpoints": true
+    },
+    {
+      "idx": 4,
+      "version": "7",
+      "when": 1784593790333,
+      "tag": "0004_true_annihilus",
+      "breakpoints": true
     }
   ]
 }