v1.17.2: bump opencode 1.16.2->1.17.2, deprecate pi, pin+patch mempalace

opencode-ai 1.16.2 -> 1.17.2 (OPENCODE_VERSION).

Deprecate all pi support ahead of v2.0.0 removal (pi now ships from the
standalone joakimp/pi-devbox image, v1.0.0+, which no longer FROMs
base-pi-only):
- build-time stderr deprecation warning when INSTALL_PI=true
- README / DOCKER_HUB.md / AGENTS.md mark the with-pi/omos-with-pi/pi-only
  variants + base-pi-only tag deprecated, point to pi-devbox
- docs/CLEANUP-v2.0.0.md committed as the removal plan
- CHANGELOG pre-announces the v2.0.0 NPM_CONFIG_PREFIX relocation

Harden mempalace install (mirrors pi-devbox):
- pin via MEMPALACE_VERSION ARG (default 3.4.0); unpinned install is what
  swept in the broken schema
- idempotent, self-deactivating patch stripping the top-level anyOf from
  mempalace_diary_write input_schema (Anthropic tools API rejects it).
  Upstream: MemPalace/mempalace#1728, PR #1735

Fold prior Unreleased smoke-test pi-extensions readiness fix into v1.17.2.

README.md

@@ -420,7 +420,8 @@ docker compose build --build-arg NVIM_VERSION=0.12.1   # pin to a specific versi
 | `INSTALL_MEMPALACE` | `true` | [MemPalace](https://github.com/MemPalace/mempalace) local AI memory system (~300 MB — disable to shrink image if you don't need MCP memory) |
 | `INSTALL_MEMPALACE_TOOLKIT` | `true` | [mempalace-toolkit](https://gitea.jordbo.se/joakimp/mempalace-toolkit) bash wrappers (`mempalace-session`, `mempalace-docs`). Cloned at build time from `MEMPALACE_TOOLKIT_REF` (default `main`). Requires `INSTALL_MEMPALACE=true`. |
 | `INSTALL_OMOS` | `false` | [oh-my-opencode-slim](https://github.com/alvinunreal/oh-my-opencode-slim) multi-agent orchestration (installs Bun and plugin) |
-| `INSTALL_OPENCODE` | `true` | Install opencode. Set `false` to build a pi-only image (still includes Bun if `INSTALL_OMOS=true`; for a fully stripped pi-only image see the `pi-devbox` repo). |
+| `INSTALL_PI` | `false` | **DEPRECATED (removed in v2.0.0)** — install pi alongside opencode. Use [`joakimp/pi-devbox`](https://gitea.jordbo.se/joakimp/pi-devbox) instead. |
+| `INSTALL_OPENCODE` | `true` | Install opencode. Set `false` to build a pi-only image (still includes Bun if `INSTALL_OMOS=true`; for a fully stripped pi-only image see the `pi-devbox` repo). **Note: the pi-only path is deprecated and removed in v2.0.0.** |
 | `INSTALL_PI` | `false` | Install [pi](https://github.com/earendil-works/pi) as alternative/complementary harness. Both clones [pi-toolkit](https://gitea.jordbo.se/joakimp/pi-toolkit) (~5 MB) and [pi-extensions](https://gitea.jordbo.se/joakimp/pi-extensions) (~1 MB) into `/opt/`; entrypoint deploys them on container start. ~150 MB total image growth. |
 | `PI_VERSION` | `latest` | npm version of `@earendil-works/pi-coding-agent`. Floats by default (image rebuild = pi update). |
 | `PI_TOOLKIT_REF`, `PI_EXTENSIONS_REF` | `main` | Git refs for the toolkit/extensions clones. Pin to a tag/commit for reproducibility. |
@@ -487,6 +488,19 @@ All six agents should respond if your provider authentication is working.
 
 ## pi (alternative/complementary harness)
 
+> **⚠ DEPRECATED since v1.17.2 — removed in v2.0.0.** pi support in
+> opencode-devbox (the `INSTALL_PI` build arg, the `*-with-pi` /
+> `omos-with-pi` / `pi-only` variants, and the `base-pi-only` tag) is
+> deprecated. pi now ships as its own self-contained image:
+> **[`joakimp/pi-devbox`](https://gitea.jordbo.se/joakimp/pi-devbox)** — pull
+> that directly. The section below documents the legacy path until removal.
+>
+> *Migration note for v2.0.0:* the global npm prefix
+> (`NPM_CONFIG_PREFIX`) will move off the pi-specific `~/.pi/npm-global`
+> path to a neutral opencode path. Globally `npm install -g`'d tools may
+> need their volume/PATH refreshed; the v2.0.0 release notes will carry a
+> one-time migration shim and details.
+
 [pi](https://github.com/earendil-works/pi) is a lightweight TUI coding-agent that can run alongside opencode in the same container. Both harnesses share the mempalace install and palace data — wing/diary entries created by one are visible to the other.
 
 ### Setup