/.well-known/mcp.json names the running version and commit, the same ones llms.txt prints #6409

Seen on production: llms.txt says "Running dev at 9bf35af" while the MCP server card says only "version": "dev", so an agent cannot tell which commit it is talking to without scraping text.

Done when:

• [ ] mcpCard (src/web/standards.ts) carries version from running() and a commit field: the full commit id, or null when unstamped. No other field changes.
• [ ] test/standards.test.ts: with FORGE_VERSION=0.7.1 and FORGE_COMMIT set, the card says both and llms.txt's running line names the same short commit; unset, the card says the unstamped version and commit: null.
• [ ] docs/MCP.md's server card section lists the new field.

Files: src/web/standards.ts, test/standards.test.ts, docs/MCP.md.

Deferred behind the Later gate (#595). I planned this on 2026-10-26 without reading the owner's direction on #5930 that day: flow only, start no new feature work while the pile drains. This is feature work, so it waits until a person opens the gate.