Tier 1.3 Phase 2: Migrate existing data to spec tables

Implements automatic population of new spec tables from existing milestone/slice/task columns.

Migration function: populateSpecTablesFromExisting()
- Runs during schema v32 migration (first database open)
- Populates milestone_specs from existing milestone table spec columns
- Populates slice_specs from existing slice table spec columns
- Populates task_specs from existing task table spec columns
- Uses INSERT OR IGNORE to safely handle existing data
- Sets spec_version to 1 for all migrated specs
- Uses current timestamp for created_at if missing

Key properties:
- Non-destructive: existing runtime rows preserved
- Idempotent: safe to re-run (INSERT OR IGNORE)
- Evidence tables left empty: populated as tools create new evidence
- Evidence populated retroactively in future phase

This completes Phase 2 of Tier 1.3. Phases 3-5 (data layer updates, tool updates, tests) follow.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/resources/extensions/sf/sf-db.js

@@ -899,6 +899,60 @@ function columnExists(db, table, column) {
 function ensureColumn(db, table, column, ddl) {
 	if (!columnExists(db, table, column)) db.exec(ddl);
 }
+function populateSpecTablesFromExisting(db) {
+	// Tier 1.3 Phase 2: Migrate existing spec data to new spec tables
+	// This populates milestone_specs, slice_specs, task_specs from existing columns
+	// Evidence tables are left empty; they populate as tools create new evidence.
+	
+	const now = new Date().toISOString();
+	
+	// Migrate milestone specs
+	db.prepare(`
+    INSERT OR IGNORE INTO milestone_specs (
+      id, vision, success_criteria, key_risks, proof_strategy,
+      verification_contract, verification_integration, verification_operational, verification_uat,
+      definition_of_done, requirement_coverage, boundary_map_markdown, vision_meeting_json,
+      spec_version, created_at
+    )
+    SELECT
+      id, vision, success_criteria, key_risks, proof_strategy,
+      verification_contract, verification_integration, verification_operational, verification_uat,
+      definition_of_done, requirement_coverage, boundary_map_markdown, vision_meeting_json,
+      1, COALESCE(created_at, ?)
+    FROM milestones
+    WHERE id NOT IN (SELECT id FROM milestone_specs)
+  `).run(now);
+	
+	// Migrate slice specs
+	db.prepare(`
+    INSERT OR IGNORE INTO slice_specs (
+      milestone_id, slice_id, goal, success_criteria, proof_level,
+      integration_closure, observability_impact,
+      adversarial_partner, adversarial_combatant, adversarial_architect,
+      planning_meeting_json, spec_version, created_at
+    )
+    SELECT
+      milestone_id, id, goal, success_criteria, proof_level,
+      integration_closure, observability_impact,
+      adversarial_partner, adversarial_combatant, adversarial_architect,
+      planning_meeting_json, 1, COALESCE(created_at, ?)
+    FROM slices
+    WHERE (milestone_id, id) NOT IN (SELECT milestone_id, slice_id FROM slice_specs)
+  `).run(now);
+	
+	// Migrate task specs
+	db.prepare(`
+    INSERT OR IGNORE INTO task_specs (
+      milestone_id, slice_id, task_id, verify, inputs, expected_output,
+      spec_version, created_at
+    )
+    SELECT
+      milestone_id, slice_id, id, verify, inputs, expected_output,
+      1, COALESCE(created_at, ?)
+    FROM tasks
+    WHERE (milestone_id, slice_id, id) NOT IN (SELECT milestone_id, slice_id, task_id FROM task_specs)
+  `).run(now);
+}
 function migrateSchema(db) {
 	const row = db.prepare("SELECT MAX(version) as v FROM schema_version").get();
 	const currentVersion = row ? row["v"] : 0;
@@ -1828,6 +1882,8 @@ function migrateSchema(db) {
 		}
 		if (currentVersion < 32) {
 			ensureSpecSchemaTables(db);
+			// Populate spec tables from existing spec columns in runtime tables
+			populateSpecTablesFromExisting(db);
 			db.prepare(
 				"INSERT INTO schema_version (version, applied_at) VALUES (:version, :applied_at)",
 			).run({