fix(#2136): route operator-facing date fields through local clock day

clock.today() derived the calendar day by slicing a UTC ISO instant
(nowIso().split('T')[0]), so in any negative-UTC-offset zone during UTC's early
hours last_activity named a day the operator had not reached yet — ahead of
last_updated's local date, written by the same call.

- Add Clock.localToday(): host-local YYYY-MM-DD via getMonth/getDate/
  getFullYear, honoring the same GSD_NOW_MS pin as today()/nowIso().
- Route operator-facing date-only fields through localToday(): last_activity
  (state-transition ×7, state.cts), roadmap 'completed <date>' (phase.cts,
  roadmap.cts), milestone completion date (milestone.cts), todo/scaffold
  completion (commands.cts — now threaded through the realClock seam).
- Leave today() (UTC) as the source for internal/cosmetic stamps.

Closes #2136

src/clock.cts

@@ -20,6 +20,8 @@ export interface Clock {
   now(): number;
   nowIso(): string;
   today(): string;
+  /** Host-local calendar day as YYYY-MM-DD — for operator-facing date-only fields. */
+  localToday(): string;
   sleep(ms: number): void;
 }
 
@@ -87,6 +89,26 @@ export const realClock: Clock = {
     return this.nowIso().split('T')[0];
   },
 
+  /**
+   * Return today's date as a YYYY-MM-DD string in the HOST-LOCAL calendar day.
+   * Uses this.now() so the subprocess time-pin adapter (GSD_NOW_MS) is honoured
+   * exactly as today()/nowIso() are — deterministic when GSD_NOW_MS and TZ are
+   * both pinned (#2136).
+   *
+   * Operator-facing date-only fields (last_activity, "completed <date>", etc.)
+   * must use the local calendar day: an operator reads them as "the day I did
+   * this", and they must never name a day ahead of `last_updated`'s local date.
+   * `today()` (UTC) stays the source for internal/cosmetic stamps.
+   *
+   * @returns e.g. "2020-06-14" (local), which may differ from today() near UTC midnight
+   */
+  localToday(): string {
+    const d = new Date(this.now());
+    const mm = String(d.getMonth() + 1).padStart(2, '0');
+    const dd = String(d.getDate()).padStart(2, '0');
+    return d.getFullYear() + '-' + mm + '-' + dd;
+  },
+
   /**
    * Synchronous sleep via Atomics.wait.
    * This is the identical primitive acquireStateLock and withPlanningLock used

src/commands.cts

@@ -42,6 +42,7 @@ const { extractFrontmatter } = frontmatter;
 import modelProfiles = require('./model-profiles.cjs');
 const { MODEL_PROFILES, VALID_PHASE_TYPES } = modelProfiles;
 import { formatGsdSlash, resolveRuntime } from './runtime-slash.cjs';
+import { realClock } from './clock.cjs';
 
 // ─── Types ────────────────────────────────────────────────────────────────────
 
@@ -1418,7 +1419,7 @@ function cmdTodoComplete(cwd: string, filename: string | undefined, raw: boolean
 
   // Read, add completion timestamp, move
   let content = fs.readFileSync(sourcePath, 'utf-8');
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.localToday();
   content = `completed: ${today}\n` + content;
 
   platformWriteSync(path.join(completedDir, filename as string), content);
@@ -1430,7 +1431,7 @@ function cmdTodoComplete(cwd: string, filename: string | undefined, raw: boolean
 function cmdScaffold(cwd: string, type: string, options: ScaffoldOptions, raw: boolean): void {
   const { phase, name } = options;
   const padded = phase ? normalizePhaseName(phase) : '00';
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.localToday();
 
   // Find phase directory
   const phaseInfo = phase ? findPhaseInternal(cwd, phase) as Record<string, unknown> | null : null;

src/milestone.cts

@@ -138,7 +138,7 @@ function cmdMilestoneComplete(cwd: string, version: string, options: MilestoneCo
   const milestonesPath = path.join(planningBase, 'MILESTONES.md');
   const archiveDir = path.join(planningBase, 'milestones');
   const phasesDir = planningPaths(cwd).phases;
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.localToday();
   const milestoneName = options.name || version;
 
   // Ensure archive directory exists

src/phase.cts

@@ -1401,7 +1401,7 @@ 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 = realClock.today();
+  const today = realClock.localToday();
 
   const phaseInfoRaw = findPhaseInternal(cwd, phaseNum);
   if (!phaseInfoRaw) {

src/roadmap.cts

@@ -497,7 +497,7 @@ function cmdRoadmapUpdatePlanProgress(cwd: string, phaseNum: string | null | und
   const verificationPassed = readVerificationStatus(phaseDir).status === 'passed';
   const isComplete = summaryCount >= planCount && verificationPassed;
   const status = isComplete ? 'Complete' : summaryCount > 0 ? 'In Progress' : 'Planned';
-  const today = realClock.today();
+  const today = realClock.localToday();
 
   if (!fs.existsSync(roadmapPath)) {
     output({ updated: false, reason: 'ROADMAP.md not found', plan_count: planCount, summary_count: summaryCount }, raw, 'no roadmap');

src/state-transition.cts

@@ -255,7 +255,7 @@ export type ProgressRecord = Record<string, unknown>;
 
 export type StateTransitionDeps = {
   progressProvider: () => ProgressRecord | null;
-  clock: { today: () => string; nowIso: () => string };
+  clock: { today: () => string; localToday: () => string; nowIso: () => string };
   /**
    * Roadmap content provider for transitions that re-derive milestone-wide
    * progress from ROADMAP.md (completePhase). Optional: transitions that don't
@@ -418,7 +418,7 @@ function beginPhaseCore(
       ? `---\n${reconstructFrontmatter(existingFm as unknown as Frontmatter)}\n---\n\n${b}`
       : b;
 
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
 
   // Consult the field-classification table for the frontmatter keys this
   // transition touches (codex Phase 1 review: "table not consulted by
@@ -721,7 +721,7 @@ function mutateCurrentPositionForAdvance(
  * adapter to construct CLI output.
  */
 function advancePlanCore(content: string, deps: StateTransitionDeps): StateTransitionResult {
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
 
   // #1255: body-field replacements operate on body only (frontmatter stripped),
   // not on the full content. The YAML `status:` key matches `^Status:\s*`
@@ -849,7 +849,7 @@ function completePhaseCore(
   deps: StateTransitionDeps,
 ): StateTransitionResult {
   const updated: string[] = [];
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
 
   // Consult the field-classification table for the frontmatter keys this
   // transition touches (same guard beginPhaseCore applies). A missing row is a
@@ -1020,7 +1020,7 @@ function plannedPhaseCore(
   deps: StateTransitionDeps,
 ): StateTransitionResult {
   const updated: string[] = [];
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
 
   for (const fmKey of ['status', 'last_activity', 'last_activity_desc']) {
     const cls = getFieldClassification(fmKey);
@@ -1124,7 +1124,7 @@ function milestoneSwitchCore(
   intent: { kind: 'milestoneSwitch'; version: string; name: string },
   deps: StateTransitionDeps,
 ): StateTransitionResult {
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
   const updated: string[] = [
     'milestone',
     'milestone_name',
@@ -1222,7 +1222,7 @@ function milestoneCompleteCore(
   deps: StateTransitionDeps,
 ): StateTransitionResult {
   const updated: string[] = [];
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
   const version = intent.version;
 
   for (const fmKey of ['status', 'last_activity', 'last_activity_desc']) {
@@ -1520,7 +1520,7 @@ function syncCore(
   intent: { kind: 'sync'; totalPlansInPhase: number | null; percent: number | null },
   deps: StateTransitionDeps,
 ): StateTransitionResult {
-  const today = deps.clock.today();
+  const today = deps.clock.localToday();
   const changes: string[] = [];
   let modified = content;
   const updated: string[] = [];

src/state.cts

@@ -2769,7 +2769,7 @@ function cmdStateCompletePhase(cwd: string, raw: boolean, overridePhase?: string
     return;
   }
 
-  const today = realClock.today();
+  const today = realClock.localToday();
   const updated: string[] = [];
 
   readModifyWriteStateMd(statePath, (content) => {