fix(extension): show Add-to-FC button on subscribed Patreon creators (#1485)

Symptom (operator-flagged): the extension injected the Add-as-source button on
a Patreon creator you had NOT subscribed to, but it disappeared once you were
subscribed — the opposite of when it's useful.

Root cause (extension logic, not Patreon security): Patreon serves a creator
under three URL shapes — bare patreon.com/Atole, patreon.com/c/Atole, and
patreon.com/cw/Atole (the 'creator workspace' URL you land on once subscribed;
documented in patreon_resolver._VANITY_RE). The button's artist-page gate
(PLATFORM_ARTIST_PATTERNS.patreon in platforms.js) and its byte-mirror probe
pattern (_PLATFORM_PATTERNS in extension_service._derive) only matched the bare
single-segment form and explicitly excluded c/. So the subscribed-view URL
failed the gate → no button. The ingestion resolver already handled all three;
only these two gates were too narrow.

Fix: both regexes now accept optional cw/ and c/ prefixes and drop the strict
single-segment end-anchor, so a creator's inner page (/cw/Atole/posts,
/Atole/membership) also matches — robust to whatever exact shape the subscribed
view uses. Nav-page exclusions (home/search/messages/notifications/library/
settings/posts + post permalinks) preserved. New unit test covers all three
prefixes, sub-paths, and nav-page rejection (both regexes validated identically).

Bump extension 1.0.7→1.0.8 so a fresh signed XPI ships the fix (also exercises
batch-5 web-ext-10's AMO sign path end-to-end on the main build).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_extension_url_derive.py

@@ -0,0 +1,65 @@
+"""Unit tests for ExtensionService._derive — the URL → (platform, slug)
+parser that gates the browser extension's "Add as source" button and pulls
+the creator slug on probe/add.
+
+Regression cover for #1485: Patreon serves the same creator under three URL
+shapes — bare `patreon.com/Atole`, `c/`, and `cw/` (the "creator workspace"
+URL you land on once SUBSCRIBED). The button used to vanish while subscribed
+because the pattern only matched the bare root and excluded `c/`.
+
+_derive is pure URL parsing (no DB / no async), so a session-less instance is
+fine to exercise directly.
+"""
+
+import pytest
+
+from backend.app.services.extension_service import (
+    ExtensionService,
+    InvalidUrlError,
+    UnknownPlatformError,
+)
+
+_svc = ExtensionService(None)
+
+
+@pytest.mark.parametrize(
+    "url, slug",
+    [
+        # All three Patreon creator prefixes resolve to the same vanity slug.
+        ("https://www.patreon.com/Atole", "Atole"),
+        ("https://www.patreon.com/c/Atole", "Atole"),
+        ("https://www.patreon.com/cw/Atole", "Atole"),  # subscribed-view URL
+        # A creator's inner page still derives the slug (trailing sub-path).
+        ("https://www.patreon.com/cw/Atole/posts", "Atole"),
+        ("https://www.patreon.com/Atole/membership", "Atole"),
+        ("https://patreon.com/c/Atole", "Atole"),  # bare host, no www
+    ],
+)
+def test_derive_patreon_creator_urls(url, slug):
+    platform, got = _svc._derive(url)
+    assert platform == "patreon"
+    assert got == slug
+
+
+@pytest.mark.parametrize(
+    "url",
+    [
+        # Patreon's own nav pages must never read as a creator slug.
+        "https://www.patreon.com/home",
+        "https://www.patreon.com/settings",
+        "https://www.patreon.com/search",
+        "https://www.patreon.com/messages",
+        "https://www.patreon.com/library",
+        "https://www.patreon.com/notifications",
+        "https://www.patreon.com/posts/12345",       # post permalink
+        "https://www.patreon.com/settings/billing",  # nav sub-page
+    ],
+)
+def test_derive_patreon_nav_pages_rejected(url):
+    with pytest.raises(UnknownPlatformError):
+        _svc._derive(url)
+
+
+def test_derive_rejects_missing_scheme():
+    with pytest.raises(InvalidUrlError):
+        _svc._derive("patreon.com/Atole")