refactor: build dogfood image as base + mise oci layers (#25448)

Splits the dogfood image into two artifacts:

- `ghcr.io/coder/oss-dogfood-base:<distro>-<base-sha>`: Ubuntu base with
apt packages, chrome, rustup, brew, gh, and the mise binary. The
base-sha is a cache key over `Dockerfile.base` and `files/`, so commits
that don't touch those inputs reuse the previous build.
- `codercom/oss-dogfood:<final-sha>-<distro>` and rolling tags
(`:22.04`, `:26.04`, `:latest`, `:<branch>`): produced by `mise oci
build` on top of the base, with one content-addressed OCI layer per mise
tool. The rolling tag scheme is unchanged, so the workspace template
doesn't need updating.

Single-tool version bumps now invalidate only that tool's OCI layer, so
workspaces re-pull just what changed instead of the entire 5-6 GB image
on every recreate.

Also:

- Drops the build-time `pnpm dlx playwright@1.47.0 install --with-deps
chromium` step (~400 MB) and the equivalent `playwright-driver.browsers`
install from `flake.nix`. `@playwright/mcp` (used by the claude-code and
codex MCP servers in `dogfood/coder/main.tf`) does NOT auto-install
browsers, so the existing `install-deps` `coder_script` now runs two
installs on workspace start: `pnpm exec playwright install chromium` for
the site's pinned `@playwright/test`, and `npx
--package=@playwright/mcp@latest playwright-core install --no-shell
chromium` so the MCP servers find their matching browser revision.
Browser revisions coexist under
`~/.cache/ms-playwright/chromium-<rev>/`, which lives on the home volume
so both downloads happen once per workspace recreate and persist across
restarts. Net effect: same MCP behavior as before, +~1-2 min on first
workspace start. Nix devshell users running site e2e tests locally now
need `pnpm exec playwright install` once (instead of getting browsers
via nixpkgs).
- Bumps the pinned mise binary to v2026.5.12 (matching main after
#25521) and adds top-level `min_version = "2026.5.12"` to `mise.toml` so
every consumer (devs, CI, the embedded mise inside the dogfood image,
mise oci builds) fails fast on an older mise.
- Adds bison, flex, libicu-dev, libreadline-dev, uuid-dev, and
zlib1g-dev to both Ubuntu base images for source-build use cases (e.g.,
building Postgres from source).
- Replaces skopeo with crane as the registry client `mise oci push`
shells out to: crane is added to `mise.toml`, the workflow drops its
`apt-get install skopeo` and forces `--tool crane`, and the local
wrapper image stops bundling skopeo. One source of truth for tool
versions, no apt drift, smaller wrapper image, and workspace users get a
registry client on PATH for free via mise oci's tool layers.
- Removes `nix.hash`/`mise.hash` and their Makefile rules. The registry
digest already captures every effective change since CI rebuilds when
any baked-in input moves; the per-file `filesha1()` entries in
`pull_triggers` are redundant.

Supersedes #25400 (the `mise.hash` pull trigger landed there in
`2b612abe7b`; this PR removes it as part of the broader simplification).

> [!NOTE]
> `mise oci build` is experimental and requires `MISE_EXPERIMENTAL=1`
(set at job level in the workflow). The local-only
`scripts/dogfood/mise-oci-wrapper.sh` builds a tiny
`coderdev/mise-oci-wrapper:<version>` Debian image with curl-installed
mise on first invocation (cached by version tag thereafter); we don't
reuse `jdxcode/mise:latest` because that tag lags upstream GitHub
releases by days and would defeat the `min_version` enforcement above.

> [!NOTE]
> `compute-base-sha.sh` and `compute-final-sha.sh` are cache keys, not
strict content addresses: the base Dockerfile still pulls dynamic
resources at build time (gh/buildx `releases/latest`, chrome
`stable_current_amd64.deb`, apt mirror state). Two runs with identical
checked-in files can produce slightly different bytes, which is
acceptable here because the cache-hit savings on irrelevant commits
outweigh that drift.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Signed-off-by: Thomas Kosiewski <tk@coder.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Makefile

@@ -1636,12 +1636,6 @@ else
 endif
 .PHONY: test-e2e
 
-dogfood/coder/nix.hash: flake.nix flake.lock
-	sha256sum flake.nix flake.lock >./dogfood/coder/nix.hash
-
-dogfood/coder/mise.hash: mise.toml mise.lock
-	sha256sum mise.toml mise.lock >./dogfood/coder/mise.hash
-
 # Count the number of test databases created per test package.
 count-test-databases:
 	PGPASSWORD=postgres psql -h localhost -U postgres -d coder_testing -P pager=off -c 'SELECT test_package, count(*) as count from test_databases GROUP BY test_package ORDER BY count DESC'