Reconcile Grace Cache Product V1 completion

[ScottArbeit]

Why this matters

Grace Cache Product V1 now has a complete Cache-required Connect path on main, but Issue #597 and the two standard
Cache documents still described earlier calibration stages as current or future work. This PR reconciles those records
with the delivered behavior so future planning starts from accurate evidence.

Closes #597

Outcome

• Replaces the Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body with the completed mainline sequence, current behavior, exact review and validation
  evidence, deferred capabilities, and a no-next-Tier-2 decision.
• Updates docs/Grace Cache.md to describe the current Product V1 purpose, delivery state, storage concurrency, loopback
  routes, fill flow, and Cache-to-WDU path.
• Updates docs/Grace Cache implementation audit.md to mark GC-CAL-02 as historical, describe the delivered Issue GC-CAL-03: Turn one Server-approved Cache miss into a verified local hit #999
  and Issue GC-CAL-04: Route one Cache-required Connect through Working Directory Update #1031 behavior, and record PR GC-CAL-04: Route Cache-required Connect through WDU #1032 repairs, revisions, validation, residual risk, and completion decision.
• Preserves all source, tests, generated files, project files, historical issues, branches, pull requests, worktrees,
  directories, and dirty state.

Baseline and scope

• Base: 05e7dd6c5fab8c2f613d9bb97c8d1395606be0c5.
• Base tree: 61bab6337f400bbeb06c71abf9ebe4eba6c04ca1.
• Delivery mode: mainline docs-only reconciliation.
• Owned repository paths: docs/Grace Cache.md and docs/Grace Cache implementation audit.md.
• Tracker write: Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body and run comments only.
• No behavior, capability, public contract, durable state, source, test, generated, or project-shape change.

Validation

• MarkdownLint on the two documents and the temporary Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body: passed with 0 errors; MD013 is ignored by
  repository policy.
• Live Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body matches the validated draft after line-ending normalization, SHA-256
  cebaa05576e6c0f87a03345c39baf94dd0a9f714ab1defbc55e9f544266f47bf.
• git diff --check: passed before and after staging.
• Local Fast, Full, build, and source tests were intentionally omitted because this change is tracker and documentation
  reconciliation only. GitHub Validate is the required broad gate for the exact PR head.

Review boundary

• R1 reviews the complete docs-only candidate against Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597, PR GC-CAL-04: Route Cache-required Connect through WDU #1032, the two documents, and the frozen write set.
• R2 runs only if R1 accepts a repair.
• Shape Review and GitHub Validate must pass on the exact reviewed head.
• Stop before merge for owner approval of that exact head.

[ScottArbeit]

Ready checkpoint

• Exact reviewed head: 0f7810b7c4e133d9913c226dd834b5a5c793d8e1.
• Base: 05e7dd6c5fab8c2f613d9bb97c8d1395606be0c5.
• R1 discovery review: PASS; the Review Discovery Ledger is empty.
• R2: not required because R1 accepted no repairs.
• Shape Review: complete; no reviewable shape change, 0 owner questions, 488 visible words, and rendered-layout checks
  passed at 1440, 1024, and 768 CSS pixels.
• Open the Shape Review.
• GitHub Validate run 32940292707: passed on the
  exact reviewed head.
• MarkdownLint passed on the two documents and the temporary Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body with 0 errors. git diff --check passed.
• The live Issue Epic: Grace Cache Factory V2 calibration and Product V1 increments #597 body matches the validated draft after line-ending normalization, SHA-256
  cebaa05576e6c0f87a03345c39baf94dd0a9f714ab1defbc55e9f544266f47bf.

The residual test omission is unchanged: no live external Server plus loopback Cache pair was run. The completed
Issue #1031 deterministic tests cover the Server-to-Cache seams and the Cache-to-staging-to-WDU composition, including
real local ZIP staging and WDU behavior.

The run is stopped before merge for owner approval of this exact reviewed and validated head. No historical Cache
issue, branch, pull request, worktree, directory, or dirty state was changed or removed.