feat(transport): Streamable HTTP mode — one shared MCP process for all sessions (v1.2.0) (#13)

* chore(ci): release fires on workflow_dispatch, not on every CI pass

Replaced workflow_run trigger (fired automatically when CI completed
on main) with workflow_dispatch. The full semantic-release automation
is preserved — bump detection, version commit, tag, GitHub Release,
NPM + Docker publish — but now runs only when explicitly triggered.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(transport): add Streamable HTTP mode — one shared process for all MCP clients (v1.2.0)

Add MCP_TRANSPORT=http mode backed by StreamableHTTPServerTransport. Each
Claude Code session connects to the shared long-lived process via HTTP (port
3031 by default) instead of spawning a new stdio process per session, eliminating
per-session process multiplication. Sessions are isolated by mcp-session-id header.

Also refactor src/index.ts to extract createMcpServer()/registerHandlers() for
clean per-session server instantiation, and upgrade fs.writeFileSync/readFileSync
calls to fs.promises async variants in export/import tool handlers.

9 new tests cover transport resolution, session isolation, teardown, and
startMcpHttpServer. All 528 tests pass. Bumps v1.1.0 → v1.2.0.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: newblacc <newblacc@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "excalidraw-mcp-sentinel",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "Hardened, self-hosted Excalidraw MCP server with SQLite persistence, multi-tenancy, auto-sync, security middleware, and 369 tests",
   "main": "dist/index.js",
   "type": "module",