fix(git-tools): scope-aware YAML fallback, port-bound creds, origin-pinned URL + review-body verification (#865)

Round-6 remediation for PR #866 addressing four cross-host exact-diff audit
blockers (REQUEST_CHANGES governs):

Blocker 1 (detect-platform.sh get_gitea_token_for_login line parser): the
PyYAML-absence fallback attributed any `key: value` at any depth to the current
login, so a token from a nested sub-map or a mis-indented line could be selected
where PyYAML fails closed, and inline comments were not stripped. The fallback is
now scope-aware — a field attaches only at the entry's own direct-field
indentation, only list items at the login list's own dash indent open an entry —
and _strip_scalar strips a trailing inline comment like PyYAML. It is therefore
only ever MORE conservative than PyYAML, never less.

Blocker 2 (detect-platform.sh host bind): credential binding compared
parsed.hostname only, dropping the port, so a :9443 login satisfied a portless
host and a matching :8443 login was rejected. Binding now normalizes scheme +
host + effective port (scheme default applied symmetrically) exactly like
gitea_url_matches_host.

Blocker 3 (issue-comment.sh + pr-review.sh read-back URL check): verification
used path.endswith, accepting a look-alike host or a decoy path prefix. It now
pins the returned issue_url/pull_request_url ORIGIN (scheme+host+effective-port)
and FULL path (deployment prefix + exact owner/repo + kind + number). A new
GITEA_WEB_BASE is exported from gitea_resolve_api_for_login for this.

Blocker 4 (pr-review.sh gitea_submit_review_verified): the submitted review body
was not verified, so a finalized/reused pending review id carrying foreign
Content passed. The persisted body is now bound to the exact submitted body.

Tests: added forced-PyYAML-absence parser-equivalence fixtures (nested sub-map,
sibling, mis-indent, inline comment, tab-indent fail-closed, port match/mismatch)
to test-gitea-login-resolution.sh; URL-forgery fail-closed cases
(wrong-host/owner/repo + prefix injection) to both write suites; and a
reused-review-id body-mismatch case to the pr-review suite.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/mosaic/framework/tools/git/test-issue-comment-readback.sh

@@ -232,13 +232,25 @@ if mode == "no-op-concurrent":
 
 author = foreign if mode == "author-mismatch" else acting
 new_id = (max((c["id"] for c in comments), default=0)) + 1
+# REAL Gitea comment shape: issue_url is the WEB (html) path, not an API path,
+# and a plain issue comment leaves pull_request_url empty. The URL-injection
+# modes persist a record whose id/author/body are all correct but whose
+# issue_url is forged, so ONLY the origin+path verification can catch them.
+issue_url = f"https://git.mosaicstack.dev/{repo}/issues/7"
+if mode == "url-wrong-host":
+    issue_url = f"https://evil.example/{repo}/issues/7"
+elif mode == "url-wrong-owner":
+    issue_url = "https://git.mosaicstack.dev/attacker/stack/issues/7"
+elif mode == "url-wrong-repo":
+    issue_url = "https://git.mosaicstack.dev/mosaicstack/other/issues/7"
+elif mode == "url-suffix-injection":
+    # Prefix-injected: a bare endswith("/<slug>/issues/7") test would ACCEPT this.
+    issue_url = f"https://git.mosaicstack.dev/deceptive/{repo}/issues/7"
 record = {
     "id": new_id,
     "body": body,
     "user": {"login": author},
-    # REAL Gitea comment shape: issue_url is the WEB (html) path, not an API
-    # path, and a plain issue comment leaves pull_request_url empty.
-    "issue_url": f"https://git.mosaicstack.dev/{repo}/issues/7",
+    "issue_url": issue_url,
     "pull_request_url": "",
 }
 comments.append(record)
@@ -491,4 +503,27 @@ if grep -q " $ACTING_LOGIN\$" "$AUTH_LOG"; then
 fi
 assert_no_temp_leak "cross-host"
 
+# Cases 7-10 (#865 Blocker 3): the created record's id/author/body are all
+# correct, but its provider-returned issue_url is forged. Verification pins the
+# URL's ORIGIN (scheme+host+effective-port) and its FULL path (deployment prefix
+# + exact owner/repo + kind + number), so each forgery must FAIL CLOSED. A bare
+# endswith/suffix test would wrongly accept the look-alike-host and
+# prefix-injection variants.
+for bad_mode in url-wrong-host url-wrong-owner url-wrong-repo url-suffix-injection; do
+    if run_comment "$bad_mode"; then
+        echo "FAIL: forged comment URL ($bad_mode) was accepted" >&2
+        cat "$OUTPUT_FILE" >&2
+        exit 1
+    fi
+    if grep -q 'Added and verified comment' "$OUTPUT_FILE"; then
+        echo "FAIL: forged comment URL ($bad_mode) passed verification" >&2
+        exit 1
+    fi
+    assert_no_temp_leak "$bad_mode"
+done
+
+# Sanity: the exact same verification path still ACCEPTS a legitimate web-shaped
+# issue_url (already exercised by Case 1's fresh-success), so the tightened check
+# is not rejecting genuine writes.
+
 echo "issue-comment.sh REST create + exact-id read-back regression passed"