docs: update sidecar binary setup, CI workflow, and troubleshooting

- CLAUDE.md: document sidecar binary strategy (download first, committed
  fallback), add curl commands for updating all 6 platform binaries,
  note PR artifact comments in CI section
- DEV.md: update sidecar section to reflect download-first strategy,
  add System Events permission prompt to troubleshooting table

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: synle

CLAUDE.md

@@ -43,7 +43,7 @@ cd src-tauri && cargo test  # Run all Rust backend tests
 
 ### CI
 
-GitHub Actions (`build.yml`) runs `npm test` and `cargo test` on all platforms (macOS ARM/Intel, Windows, Linux) for every push and PR.
+GitHub Actions (`build.yml`) runs `npm test` and `cargo test` on all platforms (macOS ARM/Intel, Windows, Linux) for every push and PR. On PRs, a comment is posted with download links for each platform's build artifacts.
 
 ## Formatting
 
@@ -85,17 +85,31 @@ These are documented inline in `config.rs` with WARNING comments.
 
 The display-dj CLI sidecar handles all platform-specific display dependencies internally. No external tools need to be installed for display control.
 
-The sidecar version is defined in `package.json` under `displayDjCliVersion`. The Rust build script (`src-tauri/build.rs`) reads this at compile time and downloads the matching release from GitHub. The `DISPLAY_DJ_CLI_VERSION` env var can override it (used by CI `workflow_dispatch`).
+### Sidecar binaries
 
-For manual builds, download from [display-dj-cli releases](https://github.com/synle/display-dj-cli/releases) or build from source:
+Pre-built sidecar binaries for all 6 platforms are committed in `src-tauri/binaries/`. The build script (`src-tauri/build.rs`) tries to download the latest from GitHub releases first, then falls back to the committed binary if the download fails (offline, timeout, etc.).
+
+The sidecar version is defined in `package.json` under `displayDjCliVersion`. The `DISPLAY_DJ_CLI_VERSION` env var can override it (used by CI `workflow_dispatch`).
+
+To update the committed binaries after a version bump, run from the project root:
 
 ```bash
-git clone https://github.com/synle/display-dj-cli.git
-cd display-dj-cli
-cargo build --release
-cp target/release/display-dj ../display-dj2/src-tauri/binaries/display-dj-server-<target-triple>
+VERSION=$(node -p "require('./package.json').displayDjCliVersion")
+cd src-tauri/binaries
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-macos-arm64" -o display-dj-server-aarch64-apple-darwin
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-macos-x64" -o display-dj-server-x86_64-apple-darwin
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-windows-x64.exe" -o display-dj-server-x86_64-pc-windows-msvc.exe
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-windows-arm64.exe" -o display-dj-server-aarch64-pc-windows-msvc.exe
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-linux-x64" -o display-dj-server-x86_64-unknown-linux-gnu
+curl -fSL "https://github.com/synle/display-dj-cli/releases/download/${VERSION}/display-dj-linux-arm64" -o display-dj-server-aarch64-unknown-linux-gnu
+chmod 755 display-dj-server-*
 ```
 
+### CI
+
+- **`build.yml`**: Runs tests and builds on all platforms for every push and PR. On PRs, posts a comment with artifact download links.
+- **`release.yml`**: Triggered by `v*` tags. Builds all platforms and uploads artifacts to a GitHub release (created as draft, publish manually).
+
 ### Linux (additional)
 
 ```bash

DEV.md

@@ -584,7 +584,9 @@ Format: `command/<action>/<value>`
 
 ## display-dj CLI Sidecar
 
-The [display-dj CLI](https://github.com/synle/display-dj-cli) is bundled as a Tauri sidecar. The version is defined in `package.json` under `displayDjCliVersion`. The build script (`src-tauri/build.rs`) downloads the matching release at compile time.
+The [display-dj CLI](https://github.com/synle/display-dj-cli) is bundled as a Tauri sidecar. The version is defined in `package.json` under `displayDjCliVersion`.
+
+Pre-built binaries for all 6 platforms are committed to the repo. The build script (`src-tauri/build.rs`) tries to download the latest from GitHub releases first (10s timeout), then falls back to the committed binary if the download fails. This enables offline builds and faster CI.
 
 ### Sidecar binaries
 
@@ -633,12 +635,13 @@ kill %1
 
 ## Troubleshooting
 
-| Problem                               | Fix                                                                                             |
-| ------------------------------------- | ----------------------------------------------------------------------------------------------- |
-| `command not found: rustc`            | Run `source "$HOME/.cargo/env"` or reopen terminal                                              |
-| First build takes 5+ minutes          | Normal. Rust compiles from source. Subsequent runs are ~5-15s                                   |
-| App launched but can't find it        | System tray app. macOS: menu bar top-right. Windows: system tray bottom-right. Linux: top panel |
-| "sidecar not found"                   | Binary missing from `src-tauri/binaries/`. See [sidecar section](#display-dj-cli-sidecar)       |
-| "server did not become ready"         | Check binary is executable (`chmod +x`), port available (`lsof -i :51337`), test directly       |
-| "No displays found"                   | Run `./src-tauri/binaries/display-dj-server-* list` directly. Linux: check `ddcutil detect`     |
-| Dark mode toggle does nothing (Linux) | Requires GNOME. Check `echo $XDG_CURRENT_DESKTOP`                                               |
+| Problem                                 | Fix                                                                                                                            |
+| --------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------ |
+| `command not found: rustc`              | Run `source "$HOME/.cargo/env"` or reopen terminal                                                                             |
+| First build takes 5+ minutes            | Normal. Rust compiles from source. Subsequent runs are ~5-15s                                                                  |
+| App launched but can't find it          | System tray app. macOS: menu bar top-right. Windows: system tray bottom-right. Linux: top panel                                |
+| "sidecar not found"                     | Binary missing from `src-tauri/binaries/`. See [sidecar section](#display-dj-cli-sidecar)                                      |
+| "server did not become ready"           | Check binary is executable (`chmod +x`), port available (`lsof -i :51337`), test directly                                      |
+| "No displays found"                     | Run `./src-tauri/binaries/display-dj-server-* list` directly. Linux: check `ddcutil detect`                                    |
+| Dark mode toggle does nothing (Linux)   | Requires GNOME. Check `echo $XDG_CURRENT_DESKTOP`                                                                              |
+| macOS "System Events" permission prompt | Expected on first launch. Volume control uses `osascript` which requires System Events access. Click Allow — only prompts once |