chore: add repo-level .mcp.json for leankg, codebase-memory-mcp, playwright

These were only registered in the user's global ~/.claude.json (with
machine-specific absolute paths), so they weren't available to anyone
else working in this repo. Added a repo-root .mcp.json using bare
command names (leankg, codebase-memory-mcp) so it's portable across
machines once those binaries are on PATH, plus the official Playwright
MCP server via npx (no install needed) — closing the "no separate
Playwright MCP server configured" gap noted in
docs/research/smart-tablet-screen-stack.md §5.

Also gitignore .leankg/ (leankg's local runtime pid/index state,
regenerated on start, not source).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tu1c13iVNdj1iWL633yazG

.gitignore

@@ -57,3 +57,6 @@
 /.claude/skills/
 /.claude/worktrees/
 
+# leankg's local runtime state (pid file, index) — regenerated on start
+/.leankg/
+

.mcp.json

@@ -0,0 +1,15 @@
+{
+  "mcpServers": {
+    "leankg": {
+      "command": "leankg",
+      "args": ["mcp-stdio", "--watch"]
+    },
+    "codebase-memory-mcp": {
+      "command": "codebase-memory-mcp"
+    },
+    "playwright": {
+      "command": "npx",
+      "args": ["-y", "@playwright/mcp@latest"]
+    }
+  }
+}

AGENTS.md

@@ -17,3 +17,13 @@ npx skills experimental_install -y
 ```
 
 No CalDAV/Nextcloud skill is pinned — none found on skills.sh fit writing a PHP backend integration (candidates were CLI personal-calendar tools or SaaS-gated); see `docs/research/smart-tablet-screen-nextcloud-todos.md` for the sabre/dav-based approach instead.
+
+### MCP servers
+
+`.mcp.json` at the repo root wires up this project's MCP servers — Claude Code loads it automatically for anyone working in this repo, no per-machine registration needed:
+
+- **`leankg`** — code-graph/knowledge-graph tooling (architecture queries, call graphs, dead-code/impact analysis). Requires the `leankg` binary on `PATH`: `cargo install leankg`.
+- **`codebase-memory-mcp`** — code-graph search and tracing (`search_graph`, `trace_path`, `get_architecture`) used per the Code Discovery Protocol below. Requires the `codebase-memory-mcp` binary on `PATH`: `pipx install codebase-memory-mcp` or `npm install -g codebase-memory-mcp`.
+- **`playwright`** — official Microsoft Playwright MCP server, run via `npx` (no install needed). Pairs with the `playwright-e2e-testing` skill and the E2E decision in `docs/research/smart-tablet-screen-stack.md` §5.
+
+`.mcp.json` uses bare command names (not absolute paths) so it works across machines once the two binaries above are installed; `playwright`'s `npx` invocation needs nothing preinstalled.