feat(eliminate-frontend-makefile): task 1.1 - Meson backend CGO test target

Adds a new `test('apiserver backend', ...)` in apiserver/meson.build
reusing the existing apiserver_cgo_deps-derived CGO flags (resolving
their @CURRENT_SOURCE_DIR@/@BUILD_ROOT@ placeholder tokens via
Meson's own .replace(), since this target invokes go_compiler
directly rather than through tools/go_build). Adds timeout: 300
(matching the existing controller test's convention) since a
cold-cache CGO+ASAN build exceeds Meson's 30s default.

Verified cold and warm cache; confirmed CGO_ENABLED=1 selects the
real backend/ CGO path, not the //go:build !cgo stub.

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

.kiro/specs/eliminate-frontend-makefile/tasks.md

@@ -1,7 +1,7 @@
 # Implementation Plan
 
 - [ ] 1. Core: CGO-backed backend test coverage via Meson
-- [ ] 1.1 (P) Add a Meson test target for the apiserver CGO-backed backend suite, reusing the existing CGO flag derivation
+- [x] 1.1 (P) Add a Meson test target for the apiserver CGO-backed backend suite, reusing the existing CGO flag derivation
   - Resolve the `@CURRENT_SOURCE_DIR@`/`@BUILD_ROOT@` placeholder tokens already present in `apiserver_cgo_deps`'s computed CGO flags at Meson-configure time (they are otherwise only resolved by `tools/go_build`'s own runtime sed machinery, which this new target does not go through)
   - Register the target with Meson's test runner (`suite: 'apiserver'`), scoped to the apiserver source directory, depending on `libxce` having already been built
   - Set the same offline/hermetic Go environment `tools/go_build` already uses (`GOFLAGS=-mod=vendor`, `GOPROXY=off`) plus an explicit, build-dir-scoped `GOCACHE`/`GOPATH` (this target invokes the Go toolchain directly, not through `go_build`, so it inherits none of `go_build`'s own internal exports)

src/frontend/apiserver/meson.build

@@ -65,3 +65,37 @@ custom_target('apiserver',
   depends: [libxce],
   install: true,
   install_dir: get_option('prefix') / 'bin')
+
+# CGO-backed backend test suite, run directly via `go test` under Meson's
+# test runner (not through tools/go_build, which only knows how to invoke
+# `go build` once for a single output). This reuses apiserver_cgo_deps's
+# already-computed cgo_cflags/cgo_ldflags (the same values the custom_target
+# above uses) rather than deriving CGO flags a second time.
+#
+# cgo_cflags/cgo_ldflags still contain the literal @CURRENT_SOURCE_DIR@/
+# @BUILD_ROOT@ placeholder tokens appended above -- normally resolved by
+# go_build's own fix_env/fix_input_envs sed machinery at build time. Since
+# this target bypasses go_build entirely, resolve those tokens ourselves at
+# Meson-configure time via Meson's own string .replace().
+resolved_cgo_cflags  = cgo_cflags.replace('@CURRENT_SOURCE_DIR@', meson.current_source_dir()).replace('@BUILD_ROOT@', meson.project_build_root())
+resolved_cgo_ldflags = cgo_ldflags.replace('@CURRENT_SOURCE_DIR@', meson.current_source_dir()).replace('@BUILD_ROOT@', meson.project_build_root())
+
+test('apiserver backend', go_compiler,
+     args:    ['test', './backend/...', '-count=1'],
+     workdir: meson.current_source_dir(),
+     env:     {'CGO_ENABLED': '1',
+               'CGO_CFLAGS': resolved_cgo_cflags,
+               'CGO_LDFLAGS': resolved_cgo_ldflags,
+               'GOFLAGS': '-mod=vendor',
+               'GOPROXY': 'off',
+               'GOCACHE': meson.current_build_dir() / 'go-cache',
+               'GOPATH': meson.current_build_dir() / 'go-path'},
+     suite:   'apiserver',
+     # A cold GOCACHE/GOPATH (the normal case: both are freshly created
+     # under this build dir, see above) makes `go test` compile the whole
+     # CGO+ASAN dependency graph from scratch -- measured ~34s, already over
+     # Meson's 30s test() default. Matches the timeout the existing
+     # 'controller test' registration uses for the same reason (see
+     # controller/meson.build / steering build-deployment.md).
+     timeout: 300,
+     depends: [libxce])