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/issue-comment.sh

@@ -254,15 +254,32 @@ from urllib.parse import urlparse
 
 
 def _origin_and_path(url):
-    # Normalize a URL to (scheme, host, effective-port) + comment path. The port
-    # defaults to the scheme's default (80 http / 443 otherwise) so an implicit
-    # port and its explicit default form compare equal.
+    # Normalize a URL to (scheme-class, host, distinguishing-port) + comment path.
+    #
+    # #991: http and https collapse into ONE scheme class ("web"). A Gitea whose
+    # ROOT_URL is configured http:// returns http:// object URLs even when every
+    # client reaches it over https://, so a scheme-strict comparison rejects the
+    # provider's own correct answer about a write that landed — a deterministic
+    # false negative on every comment posted against such a deployment. The
+    # scheme is also not what this check defends: the forgeries it exists to
+    # catch (look-alike host, decoy path prefix, wrong owner/repo/number) all
+    # vary the HOST or the PATH, both of which stay strict below. Any OTHER
+    # scheme (file:, ftp:, javascript:) remains distinguishing and is rejected.
+    #
+    # Port: an implicit port and its own scheme's default compare equal, so
+    # http://h == https://h. An EXPLICIT non-default port still distinguishes,
+    # because a different port is a different service on the same host.
     parsed = urlparse(url or "")
     scheme = (parsed.scheme or "").lower()
     host = (parsed.hostname or "").lower()
-    default_port = 80 if scheme == "http" else 443
-    port = parsed.port if parsed.port is not None else default_port
-    return (scheme, host, port), parsed.path.rstrip("/")
+    if scheme in ("http", "https"):
+        scheme_class = "web"
+        default_port = 80 if scheme == "http" else 443
+        port = None if parsed.port in (None, default_port) else parsed.port
+    else:
+        scheme_class = scheme
+        port = parsed.port
+    return (scheme_class, host, port), parsed.path.rstrip("/")
 
 
 try: