feat(eliminate-frontend-makefile): task 3.3 - update live documentation (11 files)

Removes every live current-fact reference to src/frontend/Makefile
targets or Makefile-specific fixed paths across 11 docs (steering,
frontend/CLAUDE.md, root CLAUDE.md, deployment docs, and two skill
docs), replacing with the Meson-based equivalents established by
tasks 1-3.2: /xce-build apiserver, meson test --suite apiserver,
direct tests/regression/run.sh invocation.

Round-1 review rejected the first pass: xce-deploy-ha/SKILL.md had
over-corrected by deleting all mention of deploy-ha.sh's still-real
/tmp/apiserver legacy fallback (that script's discovery logic is
unchanged, unlike run-resource-verify.sh's, which genuinely lost its
fallback in task 3.1 -- xce-test-resources/SKILL.md's identical-
looking edit was correct for that reason). Fixed by restoring an
accurate, Makefile-free description of the real fallback at all four
touched sites. Re-reviewed and approved.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XYdtrEWWZfKRRGED7raEYg

src/frontend/CLAUDE.md

@@ -11,10 +11,10 @@ Go-based REST API server (Gin) and CLI tool (Cobra) that expose cluster manageme
 
 ## Build & Test
 ```bash
-make build-server       # → /tmp/apiserver
-make build-cli          # → /tmp/xce_static (CGO_ENABLED=0, static binary)
-make test               # unit tests only (no live server required)
-make test-all           # unit + integration (needs XCE_BIN and SRV_URL env vars)
+/xce-build apiserver                              # → <build_dir>/frontend/apiserver/xce_apiserver, xcecli; runs unit tests (no live server required)
+meson test -C <build_dir> --suite apiserver       # CGO-backed backend tests
+XCE=<build_dir>/frontend/xcecli/xcecli URL=<url> \
+    tests/regression/run.sh                        # integration (needs XCE and URL env vars)
 ```
 
 ## API Server Architecture