Use Bun workspaces at plugin root + gitignore dogfood-generated paths

[ZaxShen]

Two coupled concerns

1 — Multi-package install is non-standard

Today the plugin has two independent Node packages:

• `plugin/mcp/trajectory-server/package.json`
• `plugin/monitors/package.json`

No root `package.json`. `bun install` at the repo root fails — users have to cd into each subpackage. Industry norm for monorepo-style repos is a workspace root:

```json
{
"name": "tmb-plugin",
"private": true,
"workspaces": ["mcp/trajectory-server", "monitors"]
}
```

One `bun install` at plugin root installs every subpackage, dedups shared deps (`better-sqlite3` is in both today), produces a single root `bun.lock`. `bun --filter '*' run build` builds every package that has a build script.

2 — Dogfood inside the plugin repo shouldn't pollute git

If a contributor runs CC inside the plugin repo (instead of a `/tmp/tmb-scratch`), the plugin generates:

• `.claude/tmb/trajectory.db` — already gitignored via `.claude/` ✓
• `.claude/worktrees/` — same ✓
• `docs/trustmybot/snapshots/.md` — NOT gitignored today; would track
• `docs/trustmybot/architecture/auto/*.md` + `manual/...` — NOT gitignored; would track

These are supposed to live in downstream user projects, not in the plugin repo itself. Safety net: add `docs/trustmybot/` to the plugin-root `.gitignore`. The plugin's own contributor docs live at `docs/architecture/` (not `docs/trustmybot/`), so no legitimate content is shadowed.

Proposal

1. Add `plugin/package.json` with `workspaces: ["mcp/trajectory-server", "monitors"]`.
2. Run `bun install` at plugin root to generate root `bun.lock`; delete subpackage `bun.lock` files (workspaces consolidates).
3. Add `docs/trustmybot/` to `.gitignore`.
4. Update `docs/local-testing.md` prereqs: `bun install` at plugin root (one command).
5. Update `.github/workflows/test.yml` to use root-level install.
6. Verify all 235 MCP + 16 hook + 4 lint tests pass.

Acceptance criteria

• `bun install` at plugin root installs both subpackages
• `bun run build` at plugin root builds MCP server (via workspace filter or root script)
• Subpackage `bun.lock` files removed; single root `bun.lock` committed
• `docs/trustmybot/` added to `.gitignore`
• `bash tests/run-all.sh` passes
• CI workflow updated
• `docs/local-testing.md` Prerequisites section uses the one-command form