feat(memory): dual-pool memory namespace, FTS search, and prompt injection

Add a virtual memory namespace backed by SQLite, surfaced through the
fs-tools, with private (per-user) and shared (system) stores.

Storage
- `memory_docs` owner table + external-content FTS5 index with sync triggers.
- `db/memory_docs.rs` accessor: get / upsert / list / search (bm25+snippet) / delete.

Routing (tools/fs)
- `classify_memory` splits paths on the raw first component; `..` clamps inside
  the store, never escaping to disk.
- read/write/list/edit/insert/replace/search_file route `user-memory/` to the
  owner pool and `shared-memory/` to the system pool (a singleton captured in
  `register_all`); every other path stays on disk. Each tool extracts a pure
  transform shared between its disk and memory paths.
- New `memory_search` tool over the FTS index (scope private/shared/all),
  with a sanitised FTS5 query. grep_files stays disk-only.

Approval
- `user-memory/*` allow (read+write); `shared-memory/*` reads allow,
  writes require approval so the agent can't silently push one person's data
  into shared memory. `memory_search` allowed via a path-less rule.
- migrate away the old `memory/*` and blanket `shared-memory/*` rows.

Prompt injection
- `MessageBuilder::load_inject_memory` reads `user-memory/` (owner pool) and
  `shared-memory/` (system pool) inject entries from SQLite; disk paths
  unchanged. The system pool is threaded ChatSessionManager -> handler ->
  MessageBuilder.
- main and project-coordinator inject `user-memory/index.md` +
  `shared-memory/index.md`; common/memory.md rewritten for the two stores.

agents/project-coordinator/AGENT.md

@@ -29,7 +29,7 @@ Delegate work to these task specialists via `execute_task` / `execute_subtask`:
 Your system prompt already contains, without you asking:
 
 - The project's **name**, **description**, and **working directory** (the project root — all relative file paths resolve there). You have **pre-authorized write access** to the project tree, so writing files there needs no approval.
-- **`data/memory/index.md`** — the index of the **user's personal memories** (who they are, their preferences, people, other projects). It is injected automatically. Before acting on anything personal, read the specific memory file the index points to — don't rely on the one-line summary alone.
+- **`user-memory/index.md`** and **`shared-memory/index.md`** — the indexes of your **private** memories (who the user is, their preferences, people, other projects) and the group's **shared** memories. Both are injected automatically. Before acting on anything personal, read the specific note the index points to — don't rely on the one-line summary alone.
 - **`SKALD.md`** at the project root — this project's **living diary** (see below). It is injected automatically; if it doesn't exist yet you'll see a `(file not created yet)` placeholder.
 
 Treat all of this as ground truth. If you need a detail that isn't there (for a software project: build command, test command, conventions), discover it yourself — read the project's `README`, config files, or directory with `list_files` / `read_file` — before asking the user.

agents/project-coordinator/meta.json

@@ -5,6 +5,6 @@
   "type": "chat",
   "scope": "reasoning",
   "strength": "average",
-  "inject_memory": ["data/memory/index.md", "$WD/SKALD.md"],
+  "inject_memory": ["user-memory/index.md", "shared-memory/index.md", "$WD/SKALD.md"],
   "icon": "icon.png"
 }