feat: phases + tasks — per-task execution with phase directories

- A phase is now a directory: 00_phase.md (overview + task index) plus
  small, quick NN_task.md task files; complete/ mirrors todo/
- Task is the unit of execution: run-task.sh (one unit), run-phase.sh
  (phase to completion incl. 00_phase.md final pass), auto-phase.sh
  (all units in order); validate.sh gate runs after every task
- PHASE_COMMIT commits at phase boundaries (00_phase.md / legacy file moves)
- Legacy flat todo/NN_name.md files still execute as a single unit;
  new migrate-phases-to-tasks.sh converts them to the directory layout
- phase-status.sh reports per-task state and the next unit
- New task-template.md; phase templates now carry a Tasks index

phased-execution/scripts/auto-phase.sh

@@ -1,12 +1,15 @@
 #!/usr/bin/env bash
 # auto-phase.sh — run the full phased pipeline, no LLM in the loop.
 #
-# Processes every file in .agent/phases/todo/ in alphanumerical order.
-# Each phase runs in its own pi process (fresh context); on failure the
-# executor's session is resumed for up to MAX_FIX_ATTEMPTS fixer rounds.
-# A phase moves to .agent/phases/complete/ only after the child exits 0
-# AND .agent/validate.sh passes. Stops at the first phase that cannot be
-# completed — re-run this script to continue where it stopped.
+# Processes every pending task in .agent/phases/todo/ in pipeline order
+# (phase order, then task order within each phase). Each task runs in its
+# own pi process (fresh context); .agent/validate.sh runs after EVERY task.
+# On failure the executor's session is resumed for up to MAX_FIX_ATTEMPTS
+# fixer rounds. A task moves to .agent/phases/complete/ only after the
+# child exits 0 AND validation passes; a phase completes when its
+# 00_phase.md final pass succeeds (legacy phases: when their file moves).
+# Stops at the first task that cannot be completed — re-run this script to
+# continue where it stopped.
 #
 # Env: see SKILL.md (MAX_FIX_ATTEMPTS, PHASE_MODEL, PHASE_THINKING,
 #      PHASE_COMMIT, PI_TRUST, FRESH_FIX).
@@ -16,24 +19,24 @@ source "$SCRIPT_DIR/lib.sh"
 
 # Make interruptions visible: state stays in .agent/phases/todo, and the
 # failed executor's session is still resumable on the next run.
-trap 'echo; echo "✗ ERROR: interrupted (SIGINT) — ${phase:-the pipeline} is left in $PHASE_TODO/; re-run to continue where it stopped" >&2; exit 130' INT
-trap 'echo; echo "✗ ERROR: interrupted (SIGTERM) — ${phase:-the pipeline} is left in $PHASE_TODO/; re-run to continue where it stopped" >&2; exit 143' TERM
+trap 'echo; echo "✗ ERROR: interrupted (SIGINT) — ${unit:-the pipeline} is left in $PHASE_TODO/; re-run to continue where it stopped" >&2; exit 130' INT
+trap 'echo; echo "✗ ERROR: interrupted (SIGTERM) — ${unit:-the pipeline} is left in $PHASE_TODO/; re-run to continue where it stopped" >&2; exit 143' TERM
 
 cd "$(find_root)" || die "no .agent/phases/todo found in this or parent directories (run /to-phase or /audit-create first)"
 
 build_pi_args
 delivered=()
-while phase="$(next_phase)"; do
-  [[ -n "$phase" ]] || break
-  if ! execute_phase "$phase"; then
-    echo "✗ ERROR: pipeline stopped — $phase FAILED after $MAX_FIX_ATTEMPTS attempts" >&2
+while unit="$(next_unit)"; do
+  [[ -n "$unit" ]] || break
+  if ! execute_unit "$unit"; then
+    echo "✗ ERROR: pipeline stopped — $unit FAILED after $MAX_FIX_ATTEMPTS attempts" >&2
     echo "  fix the issues above, then re-run this script to continue where it stopped" >&2
     exit 1
   fi
-  delivered+=("$phase")
+  delivered+=("$unit")
 done
 
 echo
-echo "✓ pipeline done — ${#delivered[@]} phase(s) delivered this run: ${delivered[*]:-none}"
-remaining="$(ls -1 "$PHASE_TODO" 2>/dev/null | grep -cE '^[0-9]' || true)"
-echo "  remaining in $PHASE_TODO/: $remaining"
+echo "✓ pipeline done — ${#delivered[@]} task(s) delivered this run: ${delivered[*]:-none}"
+remaining="$(count_units)"
+echo "  remaining in $PHASE_TODO/: $remaining task(s)"