v4.10.1 — copilot sessions + rtk install fallback

Added: maple now discovers GitHub Copilot CLI sessions from ~/.copilot/session-state, filtering by matching cwd in workspace.yaml. Rendered with a [gh] badge alongside Claude [cc] and OpenCode [oc]. Session detail popup parses events.jsonl for messages, tool calls, and model changes. Resume via 'o', the L launcher, or 'maple resume-session copilot' — all use 'copilot --resume='. Fixed: rtk install on linux/macos now falls back to piping the upstream install script if the GitHub release tarball approach fails (rate limit, unsupported arch, extraction error). After the upstream script exits, the Go installer searches PATH, ~/.cargo/bin, ~/.local/bin, /usr/local/bin for the binary.