Bake git commit into the binary and log it at startup

New internal/version package: ldflags-stamped Commit with a
debug.ReadBuildInfo VCS fallback for host builds. Startup log line
carries commit + Go version; --version prints the hash and exits.
Makefile computes GIT_COMMIT (12 chars, -dirty on any local change) and
passes it to docker-build/buildx; Dockerfile injects it via -ldflags and
an org.opencontainers.image.revision label. make build now uses ./cmd —
file-argument builds skip Go's automatic VCS stamp.

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

docs/plans-executions/2026-08-11-1802-bake-commit-version.md

@@ -0,0 +1,62 @@
+# Execution: Bake the git commit into the operator binary and log it at startup
+
+Plan: `docs/plans/2026-08-11-1802-bake-commit-version.md`
+
+- [x] Step 0 — Save and commit the plan
+- [x] Step 1 — `internal/version` package + tests
+- [x] Step 2 — `cmd/main.go`: `--version` flag + startup log line
+- [x] Step 3 — Makefile `GIT_COMMIT` + `--build-arg` wiring
+- [x] Step 4 — Dockerfile `-ldflags` stamp + OCI revision label
+- [ ] Step 5 — CHANGELOG entry (after the user confirms it works live)
+
+## Steps 1–4
+
+Mostly as planned. One deviation worth recording: the plan claimed
+`build`/`run` targets need no changes because Go's automatic VCS stamp covers
+host builds — that turned out to be only half true. Go skips VCS stamping
+when the build target is a *file argument* rather than a package pattern, and
+the Makefile's `build` target used `go build -o bin/manager cmd/main.go`.
+Verified empirically:
+
+```bash
+go build -o bin/manager cmd/main.go && ./bin/manager --version   # unknown (no vcs settings)
+go build -o bin/manager ./cmd       && ./bin/manager --version   # e4d2a191d0c2-dirty
+```
+
+So `build:` now uses `go build -o bin/manager ./cmd`. `go run` never stamps
+VCS info regardless of invocation form — `make run`/`run-dev` print
+`commit=unknown`, which is acceptable for dev loops (the Dockerfile path uses
+the explicit ldflags stamp and is unaffected; it kept `cmd/main.go`).
+
+The ldflags path was verified independently:
+
+```bash
+go build -ldflags "-X gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/version.Commit=deadbeef1234" \
+  -o bin/manager-stamped cmd/main.go
+./bin/manager-stamped --version   # deadbeef1234
+```
+
+Worth noting: `cmd/main.go` imports k8s apimachinery as `runtime`, so the
+stdlib runtime needed an alias (`goruntime "runtime"`) for
+`goruntime.Version()` in the startup line. The `--version` check happens
+right after `flag.Parse()`, before logger and manager setup, so it works
+without a kubeconfig.
+
+## Verification
+
+```bash
+go vet ./... && go test ./...           # all green, incl. new resolve() table tests
+go build -o bin/manager ./cmd && ./bin/manager --version   # e4d2a191d0c2-dirty
+```
+
+The image-level check could not run locally — the Docker daemon was not
+running. `make docker-build IMG=egress-proxies-operator:dev` did prove the
+Makefile side before failing at the daemon: it invoked
+`docker build --build-arg GIT_COMMIT=e4d2a191d0c2-dirty ...`. Still pending
+(needs a running daemon):
+
+```bash
+make docker-build IMG=egress-proxies-operator:dev
+docker run --rm egress-proxies-operator:dev --version
+docker inspect egress-proxies-operator:dev --format '{{index .Config.Labels "org.opencontainers.image.revision"}}'
+```