Bump opencode 1.14.44 -> 1.14.50; cut over to split-base pipeline

- Bump OPENCODE_VERSION 1.14.44 -> 1.14.50 in Dockerfile.variant
- Cut over: docker-publish-split.yml now triggers on push: tags: v*
  (was workflow_dispatch only). RELEASE_TAG and PROMOTE_LATEST derived
  from github.ref_type/ref_name for tag-push; inputs still available
  for manual workflow_dispatch runs.
- Delete docker-publish.yml (retired, replaced by split-base pipeline)
- Delete Dockerfile (retired, replaced by Dockerfile.base + Dockerfile.variant)
- Update CHANGELOG: promote Unreleased -> v1.14.50
- Update AGENTS.md, .gitea/README.md, validate.yml: remove all references
  to the old single-Dockerfile pipeline and WIP migration plan

CHANGELOG.md

@@ -8,13 +8,14 @@ Tags follow `v{opencode_version}[letter]` — bare tag for the first build on a
 
 ## Unreleased
 
-Docs:
+## v1.14.50 — 2026-05-14
 
-- **New: `.gitea/README.md`** — architectural overview of the build pipeline. Documents the production single-Dockerfile path vs the merged-but-unvalidated split-base path, hash-driven base cache reuse, wall-clock estimates, the `NPM_CONFIG_PREFIX` variant-override pattern, runner expectations (catthehacker container, disk reclaim, concurrency, gitea-actions @v4 artifact gotcha), and the cutover plan. Auto-renders when navigating to `.gitea/` in the gitea web UI. Linked from `AGENTS.md` as the first thing to read when touching CI.
+opencode 1.14.44 → 1.14.50 bump. First release on the split-base build pipeline.
 
-Build pipeline (merged to main as `Dockerfile.base` + `Dockerfile.variant` + `.gitea/workflows/docker-publish-split.yml`, NOT yet validated end-to-end — the `workflow_dispatch` test against `:base-<hash>` + `:v0.0.0-split-test*` aliases is still the gating step before this can take over `on: push: tags: v*`):
-
-- **New: split-base build pipeline.** `Dockerfile.base` (variant-independent layers — apt, locales, AWS CLI, Node.js, mempalace, gitea-mcp, user setup, chromadb prewarm, ENVs, entrypoints) builds once and is published as `joakimp/opencode-devbox:base-<sha>`. `Dockerfile.variant` `FROM`s that base and adds only opencode/omos/pi installs (or skips them per build-args). Companion workflow `.gitea/workflows/docker-publish-split.yml` runs as a `workflow_dispatch`-only pipeline alongside the existing `docker-publish.yml` so they don't conflict. Hash-driven base reuse: a content hash of `Dockerfile.base + rootfs/ + entrypoint*.sh` becomes the base tag; if the tag already exists on Docker Hub, the base build is skipped entirely. Estimated wall clock: version-bump-only release ~30–40 min (vs ~165–180 min today); base-touching release ~60–70 min. Trade-off: two Dockerfiles to maintain, and `npm install -g` in the variant must override `NPM_CONFIG_PREFIX=/usr` per-RUN to keep baked binaries off the volume-shadowed path. Once 1–2 successful workflow_dispatch runs validate the output against the existing pipeline, the new workflow takes over `on: push: tags: v*` and the original is retired.
+- **Bump:** opencode 1.14.44 → 1.14.50 (`OPENCODE_VERSION` in `Dockerfile.variant`).
+- **Infrastructure: split-base pipeline cutover.** `Dockerfile.base` + `Dockerfile.variant` replace the single `Dockerfile`. `docker-publish-split.yml` (now renamed to `docker-publish.yml` in spirit — triggers on `push: tags: v*`) replaces the old `docker-publish.yml`. The original `Dockerfile` and `docker-publish.yml` are deleted. Hash-driven base reuse: version-bump-only releases skip the base build entirely (~40–80 min wall clock with 4 runners vs ~165–180 min previously). Validated across two `workflow_dispatch` test runs (`:v0.0.0-split-test` tags on Docker Hub).
+- **Fix:** `echo -e` heredoc replaced with POSIX-compatible brace-block for multiline `$GITHUB_OUTPUT` writes in the four `build-variant-*` jobs. `echo -e` does not interpret `\n` in `/bin/sh` (dash), causing `steps.tags.outputs.tags` to be empty and buildx to fail with "tag is needed when pushing to registry".
+- **Docs:** New `.gitea/README.md` — architectural overview of the split-base pipeline, hash logic, wall-clock estimates, runner expectations, and the migration plan.
 
 ## v1.14.44 — 2026-05-09