fix: bug: TOML-driven agent services lack FACTORY_REPO env and projects/env/state volume mounts — sidecar silently never polls (#855)

In _generate_local_model_services:
- Add FACTORY_REPO environment variable to enable factory bootstrap
- Add volume mounts for ./projects, ./.env, and ./state to provide real project TOMLs

In entrypoint.sh:
- Add validate_projects_dir() function that fails loudly if no real .toml files
  are found in the projects directory (prevents silent-zombie mode where the
  polling loop matches zero files and does nothing forever)

This fixes the issue where hired agents (via hire-an-agent) ran forever without
picking up any work because they were pinned to the baked /home/agent/disinto
directory with only *.toml.example files.

lib/generators.sh

@@ -134,9 +134,13 @@ _generate_local_model_services() {
       - \${CLAUDE_CONFIG_FILE:-\${HOME}/.claude.json}:/home/agent/.claude.json:ro
       - \${CLAUDE_BIN_DIR}:/usr/local/bin/claude:ro
       - \${AGENT_SSH_DIR:-\${HOME}/.ssh}:/home/agent/.ssh:ro
+      - ./projects:/home/agent/disinto/projects:ro
+      - ./.env:/home/agent/disinto/.env:ro
+      - ./state:/home/agent/disinto/state
     environment:
       FORGE_URL: http://forgejo:3000
       FORGE_REPO: ${FORGE_REPO:-disinto-admin/disinto}
+      FACTORY_REPO: ${FORGE_REPO:-disinto-admin/disinto}
       # Per-agent credentials keyed by forge_user (#834 Gap 3).
       FORGE_TOKEN: \${FORGE_TOKEN_${user_upper}:-}
       FORGE_PASS: \${FORGE_PASS_${user_upper}:-}