fix(gsd): critical state machine data integrity fixes (wave 1/5)

Four critical fixes for the GSD state machine:

1. Event log cmd format mismatch — completion tools write hyphenated cmds
   ("complete-task") but replayEvents handled only underscored ("complete_task").
   Worktree reconciliation replay was completely broken for modern completions.
   Fix: normalize cmd via replace(/-/g, "_") in both replayEvents and
   extractEntityKey. Also adds complete_milestone replay handler and warns
   on unknown commands instead of silently skipping.

2. Dead if-block at state.ts:434-440 — empty block with misleading comments
   wasted getMilestoneSlices() + every() computation. Removed and replaced
   with clear comment explaining why all-slices-done milestones without
   SUMMARY are intentionally not added to completeMilestoneIds.

3. getActiveMilestoneId missing "skipped" status — checked complete/done/parked
   but not skipped. isStatusDone() includes skipped, creating divergence where
   a skipped milestone could become permanently "active". Fix: use
   isClosedStatus() || parked check.

4. executeReplan disk-file fallback — triage-resolution.ts writes replan
   trigger to disk and DB (best-effort). If DB write fails, deriveStateFromDb
   only checked the DB column, making the trigger invisible. Fix: fall back
   to checking the disk REPLAN-TRIGGER file when DB column is null.

src/resources/extensions/gsd/state.ts

@@ -189,7 +189,7 @@ export async function getActiveMilestoneId(basePath: string): Promise<string | n
       const byId = new Map(allMilestones.map(m => [m.id, m]));
       for (const id of sortedIds) {
         const m = byId.get(id)!;
-        if (m.status === "complete" || m.status === "done" || m.status === "parked") continue;
+        if (isClosedStatus(m.status) || m.status === "parked") continue;
         return m.id;
       }
       return null;
@@ -442,13 +442,10 @@ export async function deriveStateFromDb(basePath: string): Promise<GSDState> {
       continue;
     }
 
-    // Check roadmap: all slices done means milestone is complete
-    const slices = getMilestoneSlices(m.id);
-    if (slices.length > 0 && slices.every(s => isStatusDone(s.status))) {
-      // All slices done but no summary — still counts as complete for dep resolution
-      // if a summary file exists
-      // Note: without summary file, the milestone is in validating/completing state, not complete
-    }
+    // Milestones with all slices done but no SUMMARY file are in
+    // validating/completing state — intentionally NOT added to
+    // completeMilestoneIds.  The SUMMARY file (checked above) is the
+    // terminal artifact that proves completion per #864.
   }
 
   // Phase 2: Build registry and find active milestone
@@ -954,7 +951,12 @@ export async function deriveStateFromDb(basePath: string): Promise<GSDState> {
   // ── REPLAN-TRIGGER detection ─────────────────────────────────────────
   if (!blockerTaskId) {
     const sliceRow = getSlice(activeMilestone.id, activeSlice.id);
-    if (sliceRow?.replan_triggered_at) {
+    // Check DB column first, fall back to disk trigger file when DB write
+    // was best-effort and failed (triage-resolution.ts dual-write gap).
+    const dbTriggered = !!sliceRow?.replan_triggered_at;
+    const diskTriggered = !dbTriggered &&
+      !!resolveSliceFile(basePath, activeMilestone.id, activeSlice.id, "REPLAN-TRIGGER");
+    if (dbTriggered || diskTriggered) {
       // Loop protection: if replan_history has entries, replan was already done
       const replanHistory = getReplanHistory(activeMilestone.id, activeSlice.id);
       if (replanHistory.length === 0) {

src/resources/extensions/gsd/workflow-events.ts

@@ -19,7 +19,7 @@ export function getSessionId(): string {
 // ─── Event Types ─────────────────────────────────────────────────────────
 
 export interface WorkflowEvent {
-  cmd: string;           // e.g. "complete_task"
+  cmd: string;           // e.g. "complete-task" (canonical: hyphens; legacy: underscores — both accepted by replay)
   params: Record<string, unknown>;
   ts: string;            // ISO 8601
   hash: string;          // content hash (hex, 16 chars)

src/resources/extensions/gsd/workflow-reconcile.ts

@@ -7,6 +7,7 @@ import {
   transaction,
   updateTaskStatus,
   updateSliceStatus,
+  updateMilestoneStatus,
   getSliceTasks,
   insertVerificationEvidence,
   upsertDecision,
@@ -74,7 +75,10 @@ function replayEvents(events: WorkflowEvent[]): void {
   transaction(() => {
   for (const event of events) {
     const p = event.params;
-    switch (event.cmd) {
+    // Normalize cmd format: completion tools write hyphens ("complete-task"),
+    // legacy logs use underscores ("complete_task"). Accept both formats.
+    const cmd = event.cmd.replace(/-/g, "_");
+    switch (cmd) {
       case "complete_task": {
         const milestoneId = p["milestoneId"] as string;
         const sliceId = p["sliceId"] as string;
@@ -119,6 +123,14 @@ function replayEvents(events: WorkflowEvent[]): void {
         replaySliceComplete(milestoneId, sliceId, event.ts);
         break;
       }
+      case "complete_milestone": {
+        const milestoneId = p["milestoneId"] as string;
+        // Milestone completion via worktree replay — update status to complete
+        if (milestoneId) {
+          updateMilestoneStatus(milestoneId, "complete", event.ts);
+        }
+        break;
+      }
       case "plan_slice": {
         // plan_slice events are informational — slice should already exist.
         // No DB mutation needed during replay (the slice was inserted at plan time).
@@ -139,7 +151,7 @@ function replayEvents(events: WorkflowEvent[]): void {
         break;
       }
       default:
-        // Unknown commands are silently skipped during replay
+        logWarning("reconcile", `Unknown event cmd during replay: "${event.cmd}" — skipped`);
         break;
     }
   }
@@ -157,8 +169,10 @@ export function extractEntityKey(
   event: WorkflowEvent,
 ): { type: string; id: string } | null {
   const p = event.params;
+  // Normalize cmd format: accept both hyphens and underscores
+  const cmd = event.cmd.replace(/-/g, "_");
 
-  switch (event.cmd) {
+  switch (cmd) {
     case "complete_task":
     case "start_task":
     case "report_blocker":
@@ -172,6 +186,11 @@ export function extractEntityKey(
         ? { type: "slice", id: p["sliceId"] }
         : null;
 
+    case "complete_milestone":
+      return typeof p["milestoneId"] === "string"
+        ? { type: "milestone", id: p["milestoneId"] }
+        : null;
+
     case "plan_slice":
       return typeof p["sliceId"] === "string"
         ? { type: "slice_plan", id: p["sliceId"] }