feat(coding-agent): ResourceLoader, package management, and /reload command (#645)

- Add ResourceLoader interface and DefaultResourceLoader implementation
- Add PackageManager for npm/git extension sources with install/remove/update
- Add session.reload() and session.bindExtensions() APIs
- Add /reload command in interactive mode
- Add CLI flags: --skill, --theme, --prompt-template, --no-themes, --no-prompt-templates
- Add pi install/remove/update commands for extension management
- Refactor settings.json to use arrays for skills, prompts, themes
- Remove legacy SkillsSettings source flags and filters
- Update SDK examples and documentation for ResourceLoader pattern
- Add theme registration and loadThemeFromPath for dynamic themes
- Add getShellEnv to include bin dir in PATH for bash commands

.pi/skills/pi-tmux-test.md

@@ -1,64 +0,0 @@
----
-name: pi-tmux-test
-description: Test pi's interactive mode via tmux. Use when you need to test TUI behavior, extensions, or interactive features programmatically.
----
-
-# Testing Pi Interactively via tmux
-
-Use tmux to test pi's interactive mode. This allows sending input and capturing output programmatically.
-
-## Setup
-
-```bash
-# Kill any existing test session and create a new one
-tmux kill-session -t pi-test 2>/dev/null
-tmux new-session -d -s pi-test -c /Users/badlogic/workspaces/pi-mono -x 100 -y 30
-
-# Start pi using the test script (runs via tsx, picks up source changes)
-# Always use --no-session to avoid creating session files during testing
-tmux send-keys -t pi-test "./pi-test.sh --no-session" Enter
-
-# Wait for startup
-sleep 4
-tmux capture-pane -t pi-test -p
-```
-
-## Interaction
-
-```bash
-# Send input
-tmux send-keys -t pi-test "your message here" Enter
-
-# Wait and capture output
-sleep 5
-tmux capture-pane -t pi-test -p
-
-# Send special keys
-tmux send-keys -t pi-test Escape
-tmux send-keys -t pi-test C-c      # Ctrl+C
-tmux send-keys -t pi-test C-d      # Ctrl+D
-```
-
-## Cleanup
-
-```bash
-tmux kill-session -t pi-test
-```
-
-## Testing Extensions
-
-Write extensions to /tmp and load with `-e`:
-
-```bash
-cat > /tmp/test-extension.ts << 'EOF'
-import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
-export default function (pi: ExtensionAPI) {
-  // extension code
-}
-EOF
-
-# Run pi with the extension
-tmux send-keys -t pi-test "./pi-test.sh --no-session -e /tmp/test-extension.ts" Enter
-```
-
-Clean up after testing: `rm /tmp/test-extension.ts`