fix: pre-landing review fixes (pass 1)

Twelve informational findings from the /ship pass-1 review, all below the
blocking floor, fixed in place:

- docs-caps reads docs.caps from origin/<base>'s policy (--base <ref>), never
  the branch's copy; an unavailable base policy refuses with
  POLICY_SOURCE_UNAVAILABLE instead of substituting DEFAULT_POLICY
- receiptVersion returns "none" only when the stamp file is absent; other
  errors surface as undefined
- checkReceiptProse groups counters by leaf key and uses word boundaries that
  cover hyphenated names, so shared leaf keys and hyphenated words no longer
  report RECEIPT_PROSE_MISMATCH
- gstack-coauthor-trailers refuses a --range/--base starting with "-",
  prefixes origin/ when origin/<ref> resolves (slash-named branches), and
  passes --end-of-options to git log
- REVIEW_SCOPE_KEY_VERSION and DOCS_CAPS_KEY_VERSION name the releases that
  first read their keys
- the Step 11 late-defer row logs under skill review-late-defer so a tokenless
  review row never reads UNVERIFIED; summarizeReviewLoop counts both
- the "already filed" literal is one constant shared by bin and renderer
- receiptDocs (dead) removed
- Step 14.5 clears .gstack/tmp/docs-audit.json on first entry
- dispatched review prompts carry a literal diff-base sha (<diff-base>) instead
  of a shell variable the reviewer process never sees
- the coauthor-trailers tests launch the bin through runScriptSync so the
  Windows lane can run them

Tests extended for each change; SKILL.md, sections and goldens regenerated.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/review-policy.md

@@ -88,7 +88,7 @@ puts in the receipt:
 |---|---|
 | `review_loop.passes` | review passes this ship ran (1 to 3) |
 | `review_loop.blocking_found` | distinct blocking findings across the passes |
-| `review_loop.deferred` | blocking findings in unchanged code filed as issues (a Step 11 late defer, logged as a `review` row with `phase: late-defer`, counts here and is not a pass) |
+| `review_loop.deferred` | blocking findings in unchanged code filed as issues (a Step 11 late defer, logged as a `review-late-defer` row so it never displaces the newest `review` pass, counts here and is not a pass) |
 | `review_loop.noted` | below-floor findings listed in the PR body |
 | `review_loop.fixed` | findings fixed in this PR |
 | `review_loop.scope` | the `review_scope` the loop ran under |