fix(git): accept http/https as one scheme class in comment URL verification (#991)

issue-comment.sh and pr-review.sh verify a durable write by pinning the
provider-returned object URL's origin and full path. The origin included the
SCHEME verbatim. On a Gitea whose ROOT_URL is configured `http://` while every
client reaches it over `https://`, the provider returns `http://` object URLs,
so the comparison rejects the provider's own truthful answer about a write that
LANDED. The failure is deterministic, not intermittent: every comment, every
time, on such a deployment.

The scheme was never what the check defends. The forgeries it exists to catch —
look-alike host, decoy path prefix, wrong owner/repo/kind/number — all vary the
HOST or the PATH. Both stay strict. `http` and `https` now collapse to one
scheme class; any other scheme (file:, ftp:, javascript:) stays distinguishing,
and an EXPLICIT non-default port still distinguishes, because a different port
is a different service on the same host.

Consequences of the bug, both observed:

- The wrapper reports failure on a comment that is durably on the issue/PR, and
  attributes it to #865 ("no durable comment created"). The write landed; the
  citation is wrong. Reproduced here: the harness's persisted state contains the
  record while the wrapper exits 1.
- pr-review.sh's comment path is worse. On a host where no seat can create a
  review OBJECT, comment-form is the only gate-16 review record obtainable, and
  this check refuses all of it.

Test gap this closes: every URL fixture in both harnesses was `https://`, and
every negative case varied only host or path. The one axis that fails in
production had zero coverage — the fixtures encoded the assumption that breaks.
Added, in both suites:

- scheme-downgrade (http vs https, otherwise correct) — must be ACCEPTED. Fails
  against the unmodified wrappers, passes against the fixed ones; verified in
  both directions, and the negative control's captured output is the #865
  misattribution above.
- explicit non-default port (`:8443`) — must stay REJECTED.
- non-web scheme (`ftp://`) — must stay REJECTED.

Also fixes test-issue-comment-readback.sh hermeticity (#1007), without which the
suite cannot run on any seat that has a per-agent Gitea token: detect-platform's
step-0 identity lookup reads ~/.config/mosaic/gitea-tokens/<identity>, outside
both XDG_CONFIG_HOME and MOSAIC_CREDENTIALS_FILE, so the suite resolved a
PRODUCTION credential and died at HTTP 401 before case 1. Same two-part fix
already merged for test-pr-review-gitea-comment.sh in #1006: a sandboxed HOME
plus an empty REPO-LOCAL mosaic.gitIdentity to shadow the global. Note the
env-var route does NOT work — detect-platform.sh reads `${MOSAIC_GIT_IDENTITY:-}`
and `:-` treats set-but-empty identically to unset.

The owner-side half of #991 (setting the deployment's Gitea ROOT_URL to https)
is not in scope here and is not made unnecessary by this change; this makes the
wrappers correct against a deployment that returns either scheme.

packages/mosaic/framework/tools/git/test-pr-review-gitea-comment.sh

@@ -436,6 +436,19 @@ elif mode == "comment-url-wrong-repo":
 elif mode == "comment-url-suffix-injection":
     # Prefix-injected: a bare endswith("/<slug>/pulls/123") test would ACCEPT it.
     pr_url = f"{_origin}/deceptive{_slug}/pulls/123"
+elif mode == "comment-url-wrong-port":
+    # #991 bound: an EXPLICIT non-default port is a different service on the same
+    # host. Relaxing http-vs-https must NOT relax this.
+    pr_url = f"{_p.scheme}://{_p.hostname}:8443{_slug}/pulls/123"
+elif mode == "comment-url-non-web-scheme":
+    # #991 bound: ONLY http/https collapse; any other scheme stays distinguishing.
+    pr_url = f"ftp://{_p.netloc}{_slug}/pulls/123"
+elif mode == "comment-url-scheme-downgrade":
+    # #991, and the only URL mode here that must be ACCEPTED. A Gitea whose
+    # ROOT_URL is http:// returns http:// object URLs for a repo reached over
+    # https://. Same host, same path, correct record — a truthful provider
+    # answer about a comment that landed, not a forgery.
+    pr_url = f"http://{_p.netloc}{_slug}/pulls/123"
 elif mode == "comment-mixed-case-slug":
     # #875: EXPECTED_REPO_SLUG is taken verbatim from GITEA_API_BASE and can be
     # mixed-case (e.g. "USC/uconnect"), but Gitea canonicalizes the returned
@@ -890,11 +903,16 @@ fi
 assert_no_temp_leak "review-body-reuse"
 
 # Cases 12-15 (#865 Blocker 3): a PR comment whose id/author/body are all correct
-# but whose provider-returned pull_request_url is forged must FAIL CLOSED.
-# Verification pins the URL's ORIGIN (scheme+host+effective-port) and FULL path
-# (deployment prefix + exact owner/repo + kind + number); a bare endswith/suffix
-# test would wrongly accept the look-alike-host and prefix-injection variants.
-for bad_mode in comment-url-wrong-host comment-url-wrong-owner comment-url-wrong-repo comment-url-suffix-injection; do
+# but whose provider-returned pull_request_url does not belong to this PR must
+# FAIL CLOSED. Verification pins the URL's ORIGIN (scheme-class + host + explicit
+# non-default port) and FULL path (deployment prefix + exact owner/repo + kind +
+# number); a bare endswith/suffix test would wrongly accept the look-alike-host
+# and prefix-injection variants. comment-url-wrong-port and
+# comment-url-non-web-scheme (#991) bound the scheme relaxation from the other
+# side: collapsing http/https must not also collapse a different port or a
+# different scheme family.
+for bad_mode in comment-url-wrong-host comment-url-wrong-owner comment-url-wrong-repo \
+                comment-url-suffix-injection comment-url-wrong-port comment-url-non-web-scheme; do
     if run_review "$bad_mode" comment durable-body; then
         echo "FAIL: forged comment URL ($bad_mode) was accepted" >&2
         cat "$OUTPUT_FILE" >&2
@@ -920,6 +938,19 @@ run_review comment-mixed-case-slug comment durable-body https://git.mosaicstack.
 grep -q 'Added and verified comment on Gitea PR #123' "$OUTPUT_FILE"
 assert_no_temp_leak "comment-mixed-case-slug"
 
+# Case 15c (#991): the deployment's Gitea ROOT_URL is http:// while every client
+# reaches it over https://, so the provider returns an http:// pull_request_url
+# for a comment that is otherwise entirely correct. Same class as 15b — a
+# legitimate provider response, not a spoof — and a scheme-strict compare
+# rejects it on EVERY comment, deterministically. That is not a cosmetic false
+# negative here: on a host where no seat can create a review OBJECT, this
+# comment-form record is the only gate-16 evidence obtainable, and the wrapper
+# refuses all of it while the comment sits durably on the PR. Host, path, owner,
+# repo, kind and number stay strict; only http-vs-https is relaxed.
+run_review comment-url-scheme-downgrade comment durable-body
+grep -q 'Added and verified comment on Gitea PR #123' "$OUTPUT_FILE"
+assert_no_temp_leak "comment-url-scheme-downgrade"
+
 # Case 16 (#865 ITEM 1, current-head TOCTOU): the PR head advances between the
 # pre-submit head read (which pins the review) and the post-verify re-read. The
 # review is genuinely created and verified as pinned to the OLD head, but the