refactor: FROM opencode-devbox:latest-pi-only (lean, no opencode)

Re-point the re-brand at the new pi-only variant instead of with-pi, so
pi-devbox stays a lean pi-focused image (no opencode) while the pi install
logic still lives in one place upstream. This keeps pi-devbox meaningfully
distinct from opencode-devbox:latest-with-pi.

- Dockerfile: BASE_IMAGE default -> joakimp/opencode-devbox:latest-pi-only.
- smoke-test.sh: size threshold 2900 -> 2750 MB (pi-only = with-pi minus
  opencode's ~145 MB binary).
- Docs (README/AGENTS/DOCKER_HUB/CHANGELOG/docker-compose): drop the
  'also contains opencode' notes; describe pi-only basis and the distinction
  from with-pi.

Publish ordering unchanged: release opencode-devbox first so latest-pi-only
carries the target pi version, then tag here (smoke asserts pi --version).

AGENTS.md

@@ -1,11 +1,11 @@
 # AGENTS.md — pi-devbox
 
-Container image that re-brands the opencode-devbox **with-pi** variant as a
+Container image that re-brands the opencode-devbox **pi-only** variant as a
 pi-focused image. As of 2026-06-03 it no longer installs pi itself.
 
 ## Repository layout
 
-- `Dockerfile` — thin re-brand: `FROM opencode-devbox:latest-with-pi` (overridable via `BASE_IMAGE` arg). No install logic of its own — pi + companions are inherited from the with-pi variant. This refactor removed the install-logic duplication that used to drift against `opencode-devbox/Dockerfile.variant`.
+- `Dockerfile` — thin re-brand: `FROM opencode-devbox:latest-pi-only` (overridable via `BASE_IMAGE` arg). No install logic of its own — pi + companions are inherited from the pi-only variant (built `INSTALL_OPENCODE=false`, so **no opencode** — that's the distinction from `latest-with-pi`). This refactor removed the install-logic duplication that used to drift against `opencode-devbox/Dockerfile.variant`.
 - `docker-compose.yml` — compose file for local use
 - `.env.example` — environment variable template
 - `scripts/smoke-test.sh` — sanity checks run by CI before pushing to Docker Hub
@@ -14,12 +14,12 @@ pi-focused image. As of 2026-06-03 it no longer installs pi itself.
 ## Versioning scheme
 
 - Tags follow the pi npm version: `v{pi_version}[letter]`
-- The image inherits pi from `latest-with-pi`, so the **publish ordering matters**: rebuild opencode-devbox first so `latest-with-pi` carries the target pi version, *then* tag this repo. The smoke test asserts `pi --version` matches the tag (`EXPECTED_PI_VERSION`) and fails loudly if the base is stale.
+- The image inherits pi from `latest-pi-only`, so the **publish ordering matters**: rebuild opencode-devbox first so `latest-pi-only` carries the target pi version, *then* tag this repo. The smoke test asserts `pi --version` matches the tag (`EXPECTED_PI_VERSION`) and fails loudly if the base is stale.
 - Docker Hub: `joakimp/pi-devbox:vX.Y.Z` + `joakimp/pi-devbox:latest`
 
 ## Release-day checklist
 
-1. Ensure opencode-devbox has been released so `joakimp/opencode-devbox:latest-with-pi` carries the target pi version (and the fork/recall extensions). This is the hard prerequisite — the smoke guard enforces it.
+1. Ensure opencode-devbox has been released so `joakimp/opencode-devbox:latest-pi-only` carries the target pi version (and the fork/recall extensions). This is the hard prerequisite — the smoke guard enforces it.
 2. Update `CHANGELOG.md`: promote `Unreleased` → `vX.Y.Z — YYYY-MM-DD`
 3. Add fresh `## Unreleased` section
 4. Commit, tag `vX.Y.Z`, push tag → CI fires automatically
@@ -39,27 +39,27 @@ per version. Don't try to derive notes from the npm registry metadata
 
 ## Key facts
 
-- **Base image**: `joakimp/opencode-devbox:latest-with-pi` — the single source of truth for the pi install + companions. Rebuilt whenever opencode-devbox releases.
-- **Inherited content**: pi (`/usr/bin/pi`), pi-toolkit, pi-extensions, pi-fork (`fork`), pi-observational-memory (`recall`), the mempalace bridge, the LAN-access helper, entrypoints, and all base dev tooling. Because it FROMs with-pi, the image **also contains opencode**.
-- **Companion repos**: cloned to `/opt/` by the with-pi build; `entrypoint-user.sh` (inherited) deploys/registers them on container start.
+- **Base image**: `joakimp/opencode-devbox:latest-pi-only` — the single source of truth for the pi install + companions. Rebuilt whenever opencode-devbox releases.
+- **Inherited content**: pi (`/usr/bin/pi`), pi-toolkit, pi-extensions, pi-fork (`fork`), pi-observational-memory (`recall`), the mempalace bridge, the LAN-access helper, entrypoints, and all base dev tooling. The pi-only variant is built `INSTALL_OPENCODE=false`, so the image does **not** contain opencode.
+- **Companion repos**: cloned to `/opt/` by the pi-only build; `entrypoint-user.sh` (inherited) deploys/registers them on container start.
 - **MemPalace**: fully operational — inherited from base; bridge extension deployed by entrypoint.
 
 ## Conventions
 
 - This repo no longer installs pi or clones companion repos — do **not** re-add that logic here. Change it in `opencode-devbox/Dockerfile.variant` (the single source of truth) instead.
-- The smoke test threshold is 2900 MB (tracks the with-pi variant) — update if the image legitimately grows past it.
+- The smoke test threshold is 2750 MB (tracks the pi-only variant) — update if the image legitimately grows past it.
 - The CI still resolves the tag's pi version, but only to feed `EXPECTED_PI_VERSION` to the smoke base-freshness guard — it is no longer passed as a build-arg (nothing in the Dockerfile consumes it).
-- To pin a specific base build instead of tracking `latest-with-pi`, override the `BASE_IMAGE` arg (a version tag or a digest).
+- To pin a specific base build instead of tracking `latest-pi-only`, override the `BASE_IMAGE` arg (a version tag or a digest).
 
 ## Documentation drift sweep
 
 Before committing any non-trivial change, check that prose still matches code. Drift hotspots in this repo:
 
-- `README.md` — quick-start examples, env-var table, base-image reference (must match `FROM` in `Dockerfile`), "what's inside" (now includes opencode + fork/recall).
+- `README.md` — quick-start examples, env-var table, base-image reference (must match `FROM` in `Dockerfile`), "what's inside" (fork/recall; no opencode).
 - `AGENTS.md` (this file) — `Key facts` block (base-image tag, inherited content), smoke-test threshold number.
 - `CHANGELOG.md` — promote `Unreleased` only on tag, but record post-release fixes in a fresh `Unreleased` block.
 - `DOCKER_HUB.md` — hand-maintained slim Hub description; sync anything user-facing that changes (env vars, run command, base image).
 - `.env.example` — hand-updated, must match Dockerfile/entrypoint env vars (including the inherited LAN-access knobs).
-- `Dockerfile` `BASE_IMAGE` ARG default — the with-pi tag this image tracks.
+- `Dockerfile` `BASE_IMAGE` ARG default — the pi-only tag this image tracks.
 
 Quick triage: `git diff --name-only HEAD | xargs -I{} grep -l 'thing-you-changed' README.md AGENTS.md DOCKER_HUB.md CHANGELOG.md .env.example`.