docs(coding-agent): add PI_PACKAGE_DIR to changelog and documentation

Adds changelog entry, README env var table entry, and CLI help text for
the PI_PACKAGE_DIR environment variable added in #1153.

packages/coding-agent/CHANGELOG.md

@@ -8,6 +8,7 @@
 - Added Extension UI Protocol documentation to RPC docs covering all request/response types for extension dialogs and notifications ([#1144](https://github.com/badlogic/pi-mono/pull/1144) by [@aliou](https://github.com/aliou))
 - Added `rpc-demo.ts` example extension exercising all RPC-supported extension UI methods ([#1144](https://github.com/badlogic/pi-mono/pull/1144) by [@aliou](https://github.com/aliou))
 - Added `rpc-extension-ui.ts` TUI example client demonstrating the extension UI protocol with interactive dialogs ([#1144](https://github.com/badlogic/pi-mono/pull/1144) by [@aliou](https://github.com/aliou))
+- Added `PI_PACKAGE_DIR` environment variable to override package path for content-addressed package managers (Nix, Guix) where store paths tokenize poorly ([#1153](https://github.com/badlogic/pi-mono/pull/1153) by [@odysseus0](https://github.com/odysseus0))
 
 ### Fixed
 

packages/coding-agent/README.md

@@ -526,6 +526,7 @@ pi --thinking high "Solve this complex problem"
 | Variable | Description |
 |----------|-------------|
 | `PI_CODING_AGENT_DIR` | Override config directory (default: `~/.pi/agent`) |
+| `PI_PACKAGE_DIR` | Override package directory (useful for Nix/Guix where store paths tokenize poorly) |
 | `PI_SKIP_VERSION_CHECK` | Skip version check at startup |
 | `PI_CACHE_RETENTION` | Set to `long` for extended prompt cache (Anthropic: 1h, OpenAI: 24h) |
 | `VISUAL`, `EDITOR` | External editor for Ctrl+G |

packages/coding-agent/src/cli/args.ts

@@ -287,6 +287,7 @@ ${chalk.bold("Environment Variables:")}
   AWS_BEARER_TOKEN_BEDROCK         - Bedrock API key (bearer token)
   AWS_REGION                       - AWS region for Amazon Bedrock (e.g., us-east-1)
   ${ENV_AGENT_DIR.padEnd(32)} - Session storage directory (default: ~/${CONFIG_DIR_NAME}/agent)
+  PI_PACKAGE_DIR                   - Override package directory (for Nix/Guix store paths)
   PI_SHARE_VIEWER_URL              - Base URL for /share command (default: https://buildwithpi.ai/session/)
   PI_AI_ANTIGRAVITY_VERSION        - Override Antigravity User-Agent version (e.g., 1.23.0)