chore(#3053): clock-seam ADR-456 amendment + backfill — H2 (#3332)

* test(#3314): backfill deterministic clock-seam coverage (failing-first)

Replaces loose regex/range assertions with exact-value and boundary
tests for the CLI-subprocess and in-process clock-touching call sites
identified by H2's audit (epic #3053): cmdCurrentTimestamp,
_wsParseRetryAfter (commands.cts), cmdInitManager's is_active gate and
cmdInitQuick's quick_id generation (init.cts), and reapStaleTempFiles
(io.cts). The CLI-subprocess-pinned tests are expected RED until a
follow-up commit routes those call sites through realClock so
GSD_TEST_MODE+GSD_NOW_MS can reach them.

* refactor(#3314): route CLI-subprocess clock reads through realClock

cmdCurrentTimestamp, cmdInitManager's is_active gate, and cmdInitQuick's
quick_id generation read Date directly, which the GSD_TEST_MODE+GSD_NOW_MS
subprocess pin cannot reach (it only fires inside realClock.now()).
Behavior-preserving: realClock.now() falls through to Date.now() whenever
GSD_TEST_MODE is unset, which is every real invocation.

* docs(#3314): amend ADR-456 with reachability-based clock-control rule

ADR-456 §(a) documented one mechanism (injected {clock=Date} +
t.mock.timers). Adds the two this repo already relies on: t.mock.timers
for in-process direct-Date reads, and the GSD_TEST_MODE+GSD_NOW_MS
subprocess pin (routed through realClock) for CLI-spawned code. Updates
TESTING-STANDARDS.md's matching passages, which already referenced this
issue by number as the no-elapsed-assertion promotion precondition.

* fix(#3314): address orthogonal review findings

Spec-axis findings: file and link the no-elapsed-assertion promotion
follow-up (#3331) instead of leaving TESTING-STANDARDS.md pointing at
a dead #1885, and ship the module-by-module audit table in the ADR
itself rather than only in a gitignored phase artifact.

Standards-axis finding: pin the "hour-old file = not active" test via
GSD_TEST_MODE+GSD_NOW_MS for consistency with the reachability rule
this PR's own ADR amendment now documents.

---------

Co-authored-by: sim <sim@local>

src/commands.cts

@@ -199,7 +199,7 @@ function cmdGenerateSlug(text: string | undefined, raw: boolean): void {
 }
 
 function cmdCurrentTimestamp(format: string | undefined, raw: boolean): void {
-  const now = new Date();
+  const now = new Date(realClock.now());
   let result: string;
 
   switch (format) {

src/init.cts

@@ -1325,7 +1325,7 @@ function cmdInitQuick(
   options: Record<string, unknown> = {},
 ): void {
   const config = loadConfig(cwd);
-  const now = new Date();
+  const now = new Date(realClock.now());
   const slug = description ? generateSlugInternal(description)?.substring(0, 40) : null;
 
   const yy = String(now.getFullYear()).slice(-2);
@@ -2273,7 +2273,7 @@ function cmdInitManager(cwd: string, raw: boolean): void {
         else if (hasContext) diskStatus = 'discussed';
         else diskStatus = 'empty';
 
-        const nowMs = Date.now();
+        const nowMs = realClock.now();
         let newestMtime = 0;
         for (const f of phaseFiles) {
           try {