* feat: split server into dual ports — React SPA at :8080, Go templates at :8081

React SPA, API, SSE, and MCP are served on :8080 (default). Go template
UI moves to :8081 (-go-port flag). Both ports use /app/ as the entry
point with / redirecting there.

Key changes:
- Add goMux for Go template routes behind /app/ prefix via appHandler
- Add appPath JS variable and {{.Nav.BasePath}} for URL construction
- Vite base='/app/' for Go-served builds, '/' for dev/Tauri
- React Router basename derived from import.meta.env.BASE_URL
- API/SSE routes registered on both muxes at root level
- justfile: `just run` builds frontend+Go, `just dev` runs Go+Vite

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* docs: reorganize README around user vs developer workflows

Sections: Quick Start (run, install-claude), Desktop App (dev-tauri,
install), Development (everything else). Adds -go-port to server options.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* refactor: rename tauri -> desktop in just commands and README

`just dev-tauri` -> `just dev-desktop`, `just build-tauri` -> `just build-desktop`.
Keeps the commands implementation-agnostic.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: set VITE_API_URL for desktop production builds

The Tauri app loads frontend from disk (tauri:// protocol), so relative
API paths don't reach the Go sidecar. Set VITE_API_URL=http://localhost:8080
in the build-desktop recipe so the React app knows where to find the API.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: disable Tauri beforeBuildCommand to preserve env vars

Tauri's beforeBuildCommand was re-running `npm run build` without
VITE_BASE and VITE_API_URL, overwriting the correctly configured
frontend build from the justfile.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: remove dmg from bundle targets to avoid Finder popup on install

Only build the .app bundle since `just install` copies it directly
to /Applications.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: add CORS headers for Tauri desktop app

The production desktop app loads from tauri://localhost and fetches
the Go API at http://localhost:8080 — a cross-origin request. Without
CORS headers the browser blocks all API calls, causing a blank screen.

Allow origins matching tauri://, localhost, and 127.0.0.1.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: Cmd+Q now fully quits the desktop app and kills the sidecar

prevent_exit() was called on every ExitRequested event, so Cmd+Q
never actually quit the process — it just hid the windows while the
sidecar kept running. Now only prevent exit when windows still exist
(last-window-closed case), allowing Cmd+Q to quit properly.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: just install quits running Penpal and relaunches after install

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: properly handle macOS window close vs quit lifecycle

Use an atomic flag to distinguish "last window closed" (keep app alive
in dock) from "user quit" (Cmd+Q, dock quit). Move sidecar cleanup to
RunEvent::Exit so it runs on all exit paths.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

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Co-authored-by: Claude Opus 4.6 <[email protected]>