fix(#1161): make phase complete idempotent for roadmap completion dates (#1177)

* fix(#1161): preserve existing roadmap completion date on repeat phase complete

Guard the Completed cell write in cmdRoadmapUpdatePlanProgress so that a
non-empty, non-placeholder date is never overwritten on repeat invocations.
Also routes the date source through realClock.today() so GSD_NOW_MS pins
the written date deterministically in tests (clock seam parity with the
rest of the codebase). Regression tests added to
4-phase-complete-cjs-regression.test.cjs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#1161): preserve completion date in cmdPhaseComplete (real handler) + drive regression via phase complete CLI

- Import realClock in phase.cts; switch cmdPhaseComplete from bare `new Date()` to `realClock.today()` so the clock seam is honoured in tests
- Apply preserve-or-stamp guard to both 5-col (cells[4]) and 4-col (cells[3]) paths in cmdPhaseComplete: keep existing non-empty, non-dash date; only stamp today on first completion
- Rewrite the #1161 describe block in 4-phase-complete-cjs-regression.test.cjs to drive the real handler via runGsdTools('phase complete 1') end-to-end; cases (a)/(b)/(c)/(d) all FAIL against unfixed build and pass post-fix

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#1161): preserve only date-shaped completion cells (self-heal garbage); correct test helper for 5-col

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs(#1161): add changeset fragment for completion-date idempotence

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/phase.cts

@@ -29,6 +29,7 @@ import stateMod = require('./state.cjs');
 import { platformWriteSync, platformReadSync, platformEnsureDir } from './shell-command-projection.cjs';
 import { formatGsdSlash, resolveRuntime } from './runtime-slash.cjs';
 import { deriveProgressFromRoadmap, clampPercent } from './phase-lifecycle.cjs';
+import { realClock } from './clock.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- uat-predicate.cjs is an export= CommonJS module
 import uatPredicate = require('./uat-predicate.cjs');
 const { evaluateUatPassed } = uatPredicate;
@@ -1339,7 +1340,7 @@ function cmdPhaseComplete(cwd: string, phaseNum: string, raw: boolean): void {
   const roadmapPath = path.join(planningDir(cwd), 'ROADMAP.md');
   const statePath = path.join(planningDir(cwd), 'STATE.md');
   const phasesDir = path.join(planningDir(cwd), 'phases');
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.today();
 
   const phaseInfoRaw = findPhaseInternal(cwd, phaseNum);
   if (!phaseInfoRaw) {
@@ -1408,14 +1409,19 @@ function cmdPhaseComplete(cwd: string, phaseNum: string, raw: boolean): void {
         );
         roadmapContent = roadmapContent.replace(tableRowPattern, (fullRow) => {
           const cells = fullRow.split('|').slice(1, -1);
+          const dateShape = /^\d{4}-\d{2}-\d{2}$/;
           if (cells.length === 5) {
             cells[2] = ` ${summaryCount}/${planCount} `;
             cells[3] = ' Complete    ';
-            cells[4] = ` ${today} `;
+            // Preserve only a valid ISO date (#1161: idempotent; self-heal garbage)
+            const existingDate5 = cells[4].trim();
+            cells[4] = dateShape.test(existingDate5) ? cells[4] : ` ${today} `;
           } else if (cells.length === 4) {
             cells[1] = ` ${summaryCount}/${planCount} `;
             cells[2] = ' Complete    ';
-            cells[3] = ` ${today} `;
+            // Preserve only a valid ISO date (#1161: idempotent; self-heal garbage)
+            const existingDate4 = cells[3].trim();
+            cells[3] = dateShape.test(existingDate4) ? cells[3] : ` ${today} `;
           }
           return '|' + cells.join('|') + '|';
         });