fix: unify version comparison, refuse secret-leaking saves, reset skin strikes on card success

Fixes the three suspected bugs this PR's characterization tests pinned,
flipping those tests to assert the corrected behavior:

- plugins/store: ONE shared update comparator. New
  compatibility.is_update_available() (PEP 440 via packaging) is now used
  by both the web UI's update badge (api_v3._is_plugin_update_available
  is a thin alias) and store_manager.update_plugin's reinstall decision.
  Previously update_plugin used raw string equality: 'v1.2.0' vs '1.2.0'
  triggered a full reinstall the UI called unnecessary, and a locally-
  ahead plugin (2.0.0 installed, registry 1.9.0) was silently DOWNGRADED.
  Now equivalent spellings skip the reinstall and locally-ahead versions
  are never downgraded; unparseable versions still reconcile by
  reinstalling from the registry.

- config: save_config and save_config_atomic now refuse (ConfigError)
  when config_secrets.json exists but cannot be loaded. Both previously
  proceeded without stripping, writing the merged secrets into
  config.json in plaintext. The shared _load_secrets_for_save() helper
  raises with an actionable message instead; a missing secrets file is
  still fine (nothing to strip), and _migrate_config's catch-all keeps
  boot resilient.

- skins: render_skin_card resets _skin_failures on both success paths
  (vegas card returned, or mode renderer handled), mirroring
  _render_game. Transient card failures no longer accumulate across a
  session until they permanently disable a working skin.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NohXi78cwsAKtN1sCfxjUh

test/test_skin_system.py

@@ -455,10 +455,8 @@ class TestExampleSkin:
 class TestRenderSkinCard:
     """render_skin_card (vegas cards) shares _render_game's 3-strike counter.
 
-    The asymmetry pinned here: _render_game resets the counter on success,
-    render_skin_card does NOT — card successes never clear strikes, so
-    failures accumulated across card renders (however far apart) still
-    disable the skin for the session.
+    Both paths reset the counter on success — transient failures must not
+    accumulate across a session and disable a working skin.
     """
 
     def _probe(self, skin):
@@ -518,11 +516,10 @@ class TestRenderSkinCard:
         assert probe.builtin_calls == 1
         assert BrokenCardSkin.calls == 3  # not consulted again
 
-    def test_card_success_does_not_reset_strikes(self):
-        """Characterized asymmetry: unlike _render_game (which resets the
-        counter on success, core.py _render_game), a successful card render
-        leaves accumulated strikes in place — 2 failures + N successes + 1
-        failure still disables the skin."""
+    def test_card_success_resets_strikes(self):
+        """A successful card render clears accumulated strikes (mirroring
+        _render_game) — 2 failures + a success + 1 failure leaves the skin
+        enabled with a single strike, instead of disabling it."""
         card_img = Image.new("RGB", (96, 32), (0, 0, 255))
 
         class FlakyCardSkin(ScoreboardSkin):
@@ -540,17 +537,30 @@ class TestRenderSkinCard:
         assert probe._skin_failures == 2
 
         FlakyCardSkin.fail = False
-        for _ in range(10):
-            assert probe.render_skin_card({}, (96, 32)) is card_img
-        assert probe._skin_failures == 2  # successes did NOT clear strikes
+        assert probe.render_skin_card({}, (96, 32)) is card_img
+        assert probe._skin_failures == 0  # success cleared the strikes
 
         FlakyCardSkin.fail = True
         probe.render_skin_card({}, (96, 32))
-        assert probe._skin_failures == 3
-        assert probe.render_skin_card({}, (96, 32)) is None  # disabled
+        assert probe._skin_failures == 1  # counting from the reset state
+        FlakyCardSkin.fail = False
+        assert probe.render_skin_card({}, (96, 32)) is card_img  # still enabled
 
-    def test_render_game_success_does_reset_strikes(self):
-        """The other half of the asymmetry, for contrast with the above."""
+    def test_card_success_via_mode_renderer_also_resets_strikes(self):
+        """The fallthrough path (render_vegas_card None -> mode renderer
+        True) resets the counter as well."""
+        class ModeOnlySkin(ScoreboardSkin):
+            def render_live(self, ctx, game):
+                ctx.draw.rectangle([0, 0, 5, 5], fill=(255, 0, 0))
+                return True
+
+        probe = self._probe(ModeOnlySkin({}, {}))
+        probe._skin_failures = 2
+        assert probe.render_skin_card({}, (96, 32)) is not None
+        assert probe._skin_failures == 0
+
+    def test_render_game_success_also_resets_strikes(self):
+        """Same reset contract on the display path, for symmetry."""
         class GoodSkin(ScoreboardSkin):
             def render_live(self, ctx, game):
                 return True