fix(scripts): pr-reviews reads all three review surfaces (improvise-xgra)

It printed review BODIES only and was blind to inline review comments --
the surface a human reviewer is most likely to use. On PR #122 the user
reviewed with the body "Generally good, added comments inline." and five
substantive rulings underneath it; pr-reviews printed the one-liner, and
an agent reported the PR as awaiting review while the answers sat on it.

pulls/{n}/comments and issues/{n}/comments join pulls/{n}/reviews, all
three interleaved in time order, each inline comment carrying its path
and line (falling back to original_line, which is what an outdated
comment has left).

The exit contract is unchanged: 0 means something exists against the
current head, 1 means the wait elapsed, 4 is usage. An inline comment at
the head now satisfies --wait -- it carries a commit_id and is exactly
the case that failed. An issue-level comment does not: it names no
commit and so makes no claim about which tree was read.

The usage's exit-code warning is widened from "do not pipe into
head/tail" to the real rule: nothing may follow the script in the same
`;` list either, because a trailing `echo "exit=$?"` makes the status
the echo's.

scripts/pr-reviews-test.sh is the check_the_checker, fixture-driven and
needing no network, wired into CI's kb job beside pr-watch-test.sh and
release-preflight-test.sh. Five faults were injected and watched to
fail; context/test-evidence/tooling.md records which case caught each.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH

.github/workflows/ci.yml

@@ -273,6 +273,10 @@ jobs:
       # a tag is already public and immutable, so its refusals are checked here.
       - name: The release preflight refuses what it claims to
         run: ./scripts/release-preflight-test.sh
+      # pr-reviews is what stands between a merge and an unread review, and it
+      # was blind to inline comments for as long as it existed (improvise-xgra).
+      - name: The PR review reader refuses what it claims to
+        run: ./scripts/pr-reviews-test.sh
 
   # ---------------------------------------------------------------------------
   # Lints the one crate the `test` job cannot reach.