coder: let the omp harness drive workspaces over Coders MCP server

Coder ships `coder exp mcp server` and omp is an MCP client, so the two compose
with no custom code. The agent stays on the host where its credentials already
live and reaches into the workspace, rather than shipping secrets into a
container.

- scripts/coder-mcp.sh wraps the server, passing a dedicated `omp-mcp` token via
  `docker exec --env-file` (mode 600 temp file, shredded by an EXIT trap) so the
  token never appears in argv or ps
- allow-list exposes 26 of 32 tools; template mutation is excluded because
  pushing a template is the one real path from a Coder principal to the host
  docker socket
- scripts/coder-token-rotate.sh handles the 168h token lifetime cap: mint,
  verify against the API, then revoke the predecessors
- .omp/mcp.json registers it project-scoped so 26 tools do not load into every
  unrelated omp session

The docker exec must stay in the foreground: backgrounding it makes bash
redirect stdin from /dev/null with job control disabled, and the MCP transport
dies on EOF with "MCP tool load failed ... Transport closed".

Verified: fresh omp session in this directory answered from the tools -
coder_get_authenticated_user returned loca, workspace ws1 running.

q5vault/operations/index.md

@@ -15,7 +15,7 @@ Every command on these pages runs from `/home/loca/dev/coder` and every docker i
 | --- | --- |
 | Stack is down, needs starting, or a new image tag is out | [[operations/install-upgrade]] |
 | Someone asks why this host is not behind Authelia, or how the Owner account was bootstrapped | [[operations/auth-model]] |
-| A template needs writing or pushing, or a workspace app must be reached | [[operations/workspaces]] |
+| A template needs writing or pushing, a workspace app must be reached, or the omp harness should drive workspaces over MCP | [[operations/workspaces]] |
 | Proving the deployment is healthy after any change | [[operations/verification]] |
 | Looking up a path, container, volume, port or env var | [[reference/config-paths]] |
 | Explaining a missing feature | [[reference/limits]] |