ci: harden release pipeline and pin tooling

Un-neuter grype CVE gate (was || echo, now fails on critical).
Add .grype.yaml with ignore for CVE-2026-41589 (wish SCP —
unreachable, we only import wish/bubbletea).

Pin: grype v0.114.0, git-cliff v2.13.1, govulncheck v1.1.4.
Tag `latest` only on tag push, not workflow_dispatch.
Build path ./cmd/uptop (survives a main.go split).
Add dist/ and uptop to .dockerignore.

Dockerfile

@@ -12,7 +12,7 @@ ARG COMMIT=none
 ARG BUILD_DATE=unknown
 RUN --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
-    go build -trimpath -ldflags="-s -w -X main.version=${VERSION} -X main.commit=${COMMIT} -X main.date=${BUILD_DATE}" -o uptop ./cmd/uptop/main.go
+    go build -trimpath -ldflags="-s -w -X main.version=${VERSION} -X main.commit=${COMMIT} -X main.date=${BUILD_DATE}" -o uptop ./cmd/uptop
 
 # --- Stage 2: Runner ---
 FROM alpine:3.23@sha256:5b10f432ef3da1b8d4c7eb6c487f2f5a8f096bc91145e68878dd4a5019afde11