fix(skills): replace sqlite3 CLI with in-tree better-sqlite3 wrapper

Setup deliberately avoids the sqlite3 CLI (`setup/verify.ts:5` calls
this out: "Uses better-sqlite3 directly (no sqlite3 CLI)") and never
installs or probes for the binary. Despite that, 13 skills shelled out
to `sqlite3 ...` directly, breaking on hosts where the CLI isn't
preinstalled — the same root cause as #2191 but spread across the
skill surface.

Add `scripts/q.ts`, a ~30-LOC wrapper over the `better-sqlite3` dep
that setup already installs and verifies. Default output matches
`sqlite3 -list` (pipe-separated, no header) so existing skill text
reads identically — only the binary changes. SELECT/WITH queries go
through `db.prepare().all()`; everything else (INSERT/UPDATE/DELETE,
including compound statements) goes through `db.exec()`.

Migrate every in-tree caller:

- 17 hardcoded invocations across 8 SKILL.md files (init-first-agent,
  add-deltachat, add-signal, add-emacs, add-whatsapp, add-ollama-provider,
  debug, add-parallel) plus add-deltachat/VERIFY.md.
- `manage-channels/SKILL.md` shows canonical SQL but never prescribed
  a tool, so the assistant defaulted to `sqlite3` and silently failed.
  Add a one-line wrapper hint above the SQL block.
- `migrate-v2.sh` schema/count probes (was the original #2191 case).
  Replace `.tables` with `SELECT name FROM sqlite_master`.
- Document the wrapper convention in root `CLAUDE.md` under "Central DB".

Add `scripts/q.test.ts` with 6 vitest cases covering both modes,
NULL rendering, empty-result, compound mutations, and arg validation.
Wire `scripts/**/*.test.ts` into `vitest.config.ts`.

Out of scope (flagged for follow-up):
- `debug` and `add-parallel` still reference the v1-only path
  `store/messages.db`. Routing through the wrapper now produces a
  cleaner "no such file" error, but the surrounding sections are
  v1-era throughout — a v1-content cleanup is its own PR.
- `cleanup-sessions.sh` is being addressed in #1889 (different style,
  hard-fail rather than wrap); left untouched here to avoid stepping
  on that author's work.

Closes #2191.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -53,6 +53,8 @@ Exactly one writer per file — no cross-mount lock contention. Heartbeat is a f
 
 `data/v2.db` holds everything that isn't per-session: users, user_roles, agent_groups, messaging_groups, wiring, pending_approvals, user_dms, chat_sdk_* (for the Chat SDK bridge), schema_version. Migrations live at `src/db/migrations/`.
 
+For ad-hoc queries from skills or scripts, use the in-tree wrapper rather than the `sqlite3` CLI: `pnpm exec tsx scripts/q.ts <db> "<sql>"`. The host setup intentionally avoids depending on the `sqlite3` binary (`setup/verify.ts:5`); the wrapper goes through the `better-sqlite3` dep that setup already installs and verifies. Default-output format matches `sqlite3 -list` (pipe-separated, no header) so existing skill text reads identically.
+
 ## Key Files
 
 | File | Purpose |