feat(mcp): unpark the gitea server — it needs no AgentSecrets token

gitea-mcp was parked alongside cad on the stated reason that nothing puts its
token into the session environment: GITEA_MCP_STATIC_TOKEN lives in the
AgentSecrets vault, which the session identity deliberately cannot read
(infra#224), so enabling it was blocked behind #32/#33.

That reason never applied to gitea. gitea-mcp authenticates by PASS-THROUGH:
the bearer is a Gitea PAT, which the server validates against Gitea and then
acts as. No dedicated MCP token exists to be missing. DMABE_GITEA_API_TOKEN is
op://HomeLab and already in the session environment.

Verified on koala 2026-09-07 against tailscale serve 8446 -> NodePort 30340:
initialize returns 200 with serverInfo gitea-mcp, tools/list returns 41 tools.
Two DIFFERENT PATs both authenticate while GITEA_MCP_TOKEN 401s -- that is what
proves pass-through validation rather than a static-token comparison, and it
also shows GITEA_MCP_TOKEN is stale (it 401s against git-mcp.d-ma.be too).

cad stays parked; its blocker is real and unchanged.

Also adds bin/check-mcp-env and tests/mcp_config_test.sh, wired into task check.
The fault it gates is silent: a header interpolating an undefined variable does
not error, it sends an empty Authorization, and Claude Code reports "requires
authentication" -- indistinguishable from a revoked credential. That cost a full
investigation on koala today before the credential turned out to be fine. The
check exits 2 rather than 0 when it cannot run (no jq, no env-file, as in CI),
so an unverified config is never reported as a clean one. Servers under _parked
are exempt: referencing an unprovided variable is what parked means.

Bump-Type: minor

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Taskfile.yml

@@ -138,6 +138,21 @@ tasks:
           echo "ERROR: missing .claude-plugin/plugin.json" >&2; fail=1
         fi
 
+        # Every ${VAR} a live .mcp.json server interpolates must be one the
+        # session env-file defines. An undefined one is silent: the header
+        # goes out empty and the server reports "requires authentication",
+        # which reads as a revoked credential. Exit 2 means the check could
+        # not run (no jq, or no env-file — CI has neither); that is reported
+        # and not fatal, but it is never treated as a pass.
+        if [ -x "{{.TASKFILE_DIR}}/bin/check-mcp-env" ]; then
+          "{{.TASKFILE_DIR}}/bin/check-mcp-env" "{{.TASKFILE_DIR}}/.mcp.json" "$HOME/.op-env"
+          case $? in
+            0) ;;
+            2) echo "NOTE: MCP env wiring unverified on this host" >&2 ;;
+            *) fail=1 ;;
+          esac
+        fi
+
         if [ $fail -ne 0 ]; then
           echo "check FAILED" >&2; exit 1
         fi