v2.12.0

Unattended auto-mode hardening (Phase 45). Makes --mode auto launchable and safe out of the box:
a configurable git-flow trunk so a phase worktree can fork from a personal .planning/-tracking
branch instead of hardcoded develop, a self-dogfood staleness check scoped to actual Cargo
workspace members, and a shared unattended-decision policy for the Code stage.

Added

• configurable base branch (base_branch in devflow.toml, or DEVFLOW_BASE_BRANCH), resolved
  once and shared by the worktree fork point, the merge target, and every later process
  (advance/resume/the monitor/ship evidence) that needs to agree on the same trunk
• affects_compiled_binary scoped to Cargo workspace members plus root build files (including
  .cargo/config.toml) for DevFlow's own self-dogfood check, so .planning/spikes/ no longer
  trips a false stale-build block; every other project DevFlow drives keeps its prior repo-wide rule
• a shared CODE_STAGE_POLICY instructing the agent to evaluate unattended decision checkpoints
  on merit and record its reasoning, delivered to both agent-family Code-stage renderers on the
  first pass

Fixed

• the base-branch substitution's blast radius: cleanup_merged could delete the built-in develop/
  main trunks under a configured base, and the resolved base was not persisted, so a later
  resume in a fresh shell silently fell back to develop for the worktree base, the idle-timeout
  commit evidence, and the Ship merge-evidence check — each fixed to consult the run's own recorded
  base
• a devflow.toml that fails to parse no longer silently falls back to the default trunk; the
  base-branch resolver's fail-hard contract now covers a bad file, not only a bad value

Known gap

• the unattended-decision policy does not yet reach the Claude/OpenCode loop-back Code prompt
  (fix_prompt's FullExecute arm), so a run that fails Validate and retries under that path gets
  no policy while the Codex/Pi equivalent does. Confirmed in shipped source by an internal review
  and two independent external reviews; accepted as this release's terminal state for that one path
  rather than reopening the plan — tracked as backlog 999.115 and 999.116.