fix: write valid multi-line tmux config in Pi Agent images

The Pi Agent dockerfile templates created ~/.tmux.conf with a literal
\n because the RUN command used single-quoted echo. Tmux never parsed
the malformed line, so mouse mode stayed off. Without tmux mouse mode,
mouse-wheel events in xterm.js fell back to Up/Down arrow keys and
cycled shell command history instead of scrolling the terminal buffer.

- Use printf '%s\n' to write real newlines in .tmux.conf.
- Apply the same fix to the ranger rc.conf where the same bug existed.
- Update tool-images/pi-agent.dockerfile and both affected alembic
  migration dockerfile strings.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (87 passed),
py_compile on changed migrations.

Refs: openspec/changes/fix-tmux-mouse-config

.pi-map.index.md

@@ -16,7 +16,7 @@ dir: .
 Trust boundary: index routes, map orients, source decides.
 
 ## role
-A self-hosted web-based project management and git repository platform with OAuth2 authentication, built as a containerized multi-service application with PostgreSQL, Redis, and Traefik deployment support.
+Infrastructure and deployment configuration for a self-hosted project management platform with OAuth2 authentication, providing Docker Compose orchestration, environment templates, and development tooling.
 ## parent
 -
 ## children