feat: add process logging with DAG-based event sourcing

Event-sourced orchestration logging: JSONL events with parent
relationships form a DAG for causal reconstruction of agent flows.
Includes bash event emitter (jq-based) and markdown report generator.

skills/orchestration/SKILL.md

@@ -62,6 +62,33 @@ Guardian completes  → A2 (fast-path check) → if clean, skip other reviewers
 Check phase done    → A1 (escalation check) → if 2+ CRITICALs in fast, next cycle is standard
 ```
 
+## Process Logging
+
+If `.archeflow/events/` exists (or should be created), emit structured events throughout orchestration. See `archeflow:process-log` skill for full schema.
+
+**Quick reference — emit at these points:**
+
+```
+run.start        → After workflow selection, before first agent
+agent.start      → Before each Agent tool call
+agent.complete   → After each Agent returns (include duration, tokens, summary, artifacts)
+decision         → When choosing between alternatives (plot direction, approach, fix strategy)
+phase.transition → At Plan→Do, Do→Check, Check→Act boundaries
+review.verdict   → After each reviewer delivers verdict
+fix.applied      → After each edit addressing a review finding
+cycle.boundary   → End of PDCA cycle
+shadow.detected  → When shadow threshold triggers
+run.complete     → After final Act phase (include totals)
+```
+
+**Helper:** `./lib/archeflow-event.sh <run_id> <type> <phase> <agent> '<json>'`
+
+**Report:** `./lib/archeflow-report.sh .archeflow/events/<run_id>.jsonl`
+
+Events are optional — if the events dir doesn't exist, skip logging. Never let logging block orchestration.
+
+---
+
 ## Step 1: Plan Phase
 
 Spawn agents sequentially — Creator needs Explorer's findings.
@@ -409,7 +436,9 @@ After each task completes (success or failure):
 
 ### Session Log Protocol
 
-Write to `.archeflow/session-log.md` after each task:
+**Primary:** Emit `run.complete` event to `.archeflow/events/<run_id>.jsonl` (see Process Logging section above). The event stream is the source of truth.
+
+**Secondary:** Also write a human-readable summary to `.archeflow/session-log.md`:
 
 ```markdown
 ## Task N: <description>
@@ -419,8 +448,11 @@ Write to `.archeflow/session-log.md` after each task:
 **Files changed:** 5 | **Tests added:** 12
 **Branch:** merged to main (commit abc1234) | OR: archeflow/maker-xyz (NOT merged)
 **Duration:** 8 min
+**Events:** `.archeflow/events/<run_id>.jsonl` (full process log)
 ```
 
+Generate the full Markdown report: `./lib/archeflow-report.sh .archeflow/events/<run_id>.jsonl`
+
 ### Safety Rules
 - Never force-push. Never modify main history.
 - All work stays on worktree branches until explicitly merged