fix: Implement warm start pattern for session restoration (v2.19.5)

Fixes critical bug where synthetic MCP initialization had no HTTP context
to respond through, causing timeouts. Implements warm start pattern that
handles the current request immediately.

Breaking Changes:
- Deleted broken initializeMCPServerForSession() method (85 lines)
- Removed unused InitializeRequestSchema import

Implementation:
- Warm start: restore session → handle request immediately
- Client receives -32000 error → auto-retries with initialize
- Idempotency guards prevent concurrent restoration duplicates
- Cleanup on failure removes failed sessions
- Early return prevents double processing

Changes:
- src/http-server-single-session.ts: Simplified restoration (lines 1118-1247)
- tests/integration/session-restoration-warmstart.test.ts: 9 new tests
- docs/MULTI_APP_INTEGRATION.md: Warm start documentation
- CHANGELOG.md: v2.19.5 entry
- package.json: Version bump to 2.19.5
- package.runtime.json: Version bump to 2.19.5

Testing:
- 9/9 new integration tests passing
- 13/13 existing session tests passing
- No regressions in MCP tools (12 tools verified)
- Build and lint successful

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

AGENTS.md

@@ -0,0 +1,24 @@
+# Repository Guidelines
+
+## Project Structure & Module Organization
+The MCP integration is centered in `src/`: orchestration in `src/mcp`, engine helpers in `src/services`, and shared contracts in `src/types`. Built artifacts and the CLI wrapper land in `dist/`. Tests are grouped under `tests/` (unit, integration, e2e), while deployment aids and references live in `deploy/`, `docs/`, and `scripts/`. Template catalogs and sample data reside in `templates/` and `data/`.
+
+## Build, Test, and Development Commands
+- `npm run build` – transpile TypeScript with `tsconfig.build.json` into `dist/`.
+- `npm run dev` – rebuilds sources, refreshes templates, and validates packaging.
+- `npm run start:http` / `npm run start:n8n` – boot the MCP server in HTTP or n8n modes.
+- `npm run test` – execute Vitest; `npm run test:integration` and `npm run test:e2e` scope coverage.
+- `npm run lint` (alias `npm run typecheck`) – verify types without emitting artifacts.
+- `npm run test:coverage` – generate coverage reports in `coverage/`.
+
+## Coding Style & Naming Conventions
+Code is TypeScript-first with ES modules. Follow the prevalent two-space indentation, single quotes, and trailing commas for multi-line literals. Prefer named exports, keep HTTP entry points under `src/http-server*`, and collocate helper utilities inside `src/utils`. Use `PascalCase` for classes, `camelCase` for functions and variables, and `SCREAMING_SNAKE_CASE` for shared constants. Rebuild before committing so `dist/` mirrors `src/`.
+
+## Testing Guidelines
+Vitest drives all automated testing. Place new suites beside peers using the `*.test.ts` suffix (for example, `tests/unit/session-restoration.test.ts`). Integration and end-to-end suites depend on the sample SQLite stores in `data/` and may invoke `docker/` assets; use `npm run test:integration`, `npm run test:mcp-endpoint`, or `npm run test:e2e` when validating those flows. Track coverage with `npm run test:coverage` and call out notable gaps in the PR.
+
+## Commit & Pull Request Guidelines
+History favors Conventional Commit prefixes (`fix:`, `feat:`, `chore:`) with optional release tags and issue links (`(#123)`). Keep subjects under 72 characters and describe breaking changes in the body. Pull requests should deliver a short summary, curl traces or screenshots for interface updates, reproduction steps, and links to issues or deployments. Run `npm run dev` plus targeted `npm run test:*` commands before requesting review.
+
+## Environment & Configuration Tips
+Copy secrets from `.env.example` when bootstrapping. Template catalogs rely on the bundled SQLite databases under `data/`; refresh them with `npm run rebuild` or `npm run fetch:templates`. For search features, run `npm run prebuild:fts5` before rebuilding so native FTS5 bindings are available.