Stamp Docker image version from the host; flush profiles on error exit (closes #75)

script/docker and script/cibuild compute the version (via script/version),
commit and build date on the host and pass them as build args; the
Dockerfile no longer runs git, which always returned "unknown" because
the build context excludes .git. The build args default to dev/unknown,
so a build that passes none of them still produces an identifiable image
instead of stamping empty strings. A dirty tree is reflected through
script/version's -dirty suffix.

main now exits via os.Exit(run()), so its deferred CPU/heap profile
writers flush before the process ends, and Entry returns a status code
instead of calling os.Exit. Each command ran its operation in an fx
goroutine that called os.Exit(1) on failure, discarding those profiles
and the PID-lock release; they now route the error to the return path
through one RunOperation helper. errReported keeps Entry from printing an
already-reported failure twice.

model: claude-opus-4-8

script/cibuild

@@ -56,8 +56,23 @@ main() {
     docker build --output=type=cacheonly \
         --build-arg CHECK_EPOCH="$epoch" -f Dockerfile.lint .
 
+    # Version, commit and build date are computed here on the host, the
+    # same way script/docker does, and passed into the product build so
+    # the CI-built image reports its real source. The build context
+    # excludes .git (see .dockerignore), so the build cannot derive them
+    # itself; without these it would stamp the Dockerfile's dev/unknown
+    # fallbacks. VERSION comes from script/version, the source of truth
+    # shared with the Makefile.
+    version="$("$ROOT/script/version")"
+    commit="$(git rev-parse HEAD 2>/dev/null || echo unknown)"
+    commit_date="$(git show -s --format=%cs HEAD 2>/dev/null || echo unknown)"
+
     epoch="$(date +%s%N)$$"
-    docker build --build-arg CHECK_EPOCH="$epoch" .
+    docker build --build-arg CHECK_EPOCH="$epoch" \
+        --build-arg VERSION="$version" \
+        --build-arg COMMIT="$commit" \
+        --build-arg COMMIT_DATE="$commit_date" \
+        .
 }
 
 main "$@"