fix(extensions): stop env-var config leaking across prefix-colliding extension IDs (#3497)

* fix(extensions): stop env-var config leaking across prefix-colliding IDs (#3494)

Because ``_`` doubles as both the separator between an extension ID and
its config path AND the substitute for ``-`` inside an extension ID, an
env var like ``SPECKIT_GIT_HOOKS_URL`` starts with *both* the
``SPECKIT_GIT_`` prefix of the ``git`` extension and the
``SPECKIT_GIT_HOOKS_`` prefix of a co-installed ``git-hooks`` extension.
``ConfigManager._get_env_config`` matched only on the shorter prefix,
so the same env var silently surfaced inside both extensions' configs
(as ``{'hooks': {'url': ...}}`` for ``git`` and ``{'url': ...}`` for
``git-hooks``).

Impact: config intended for one extension leaked into another and, worse,
could flip ``config.<field> is set`` hook conditions on the wrong
extension.

Route the env var to the extension whose normalized ID is the longest
match — the more specific one. When another installed sibling's
normalized ID + ``_`` claims the remainder, skip the var here. The
sibling scan reads ``.specify/extensions/`` directly and degrades to a
no-op if the dir is missing (fresh project / ad-hoc harness), so the
pre-fix single-extension behaviour is unchanged when there is no
collision.

Distinct from #3350 (intra-extension prefix collision between two keys
of the same extension) — this fixes the cross-extension case.

Fixes #3494

* fix(extensions): source sibling scan from registry, not directory

Address Copilot review on #3497: ``ExtensionManager.remove(...,
keep_config=True)`` preserves the extension directory but drops the
registry entry, so the previous directory-scan approach would treat a
config-only leftover as an installed sibling and silently discard
``SPECKIT_<sibling>_*`` env vars into no owner. Sourced the sibling
list from ``ExtensionRegistry.keys()`` — the registry is the source of
truth for "installed" — and kept the same graceful ``[]`` fallback so
the fresh-project / ad-hoc harness path is unaffected. Updated the
``TestConfigManagerCrossExtensionEnvLeak`` ``_install`` helper to
register its fake installations and added
``test_config_only_leftover_not_treated_as_sibling`` to lock in the
new behaviour for the ``keep_config=True`` scenario.

Full suite: 3978 passed, 110 skipped.

* fix(extensions): swallow non-UTF-8 registry in sibling scan

Address Copilot follow-up on #3497: ``ExtensionRegistry._load()`` catches
``JSONDecodeError`` / ``FileNotFoundError`` but not decode failures — a
registry file with invalid text encoding would surface a
``UnicodeDecodeError`` out of ``_sibling_extension_ids`` and break every
config read instead of degrading to the documented pre-fix behaviour.
Extend the fallback in ``_sibling_extension_ids`` to also catch
``UnicodeError`` and add ``test_non_utf8_registry_does_not_crash`` as a
regression pin (kept ``_load()`` itself out of scope — that broader
hardening belongs in a separate PR since it affects all readers).

Full suite: 3979 passed, 110 skipped.

src/specify_cli/extensions/__init__.py

@@ -2737,6 +2737,36 @@ class ConfigManager:
         config_file = self.extension_dir / "local-config.yml"
         return self._load_yaml_config(config_file)
 
+    def _sibling_extension_ids(self) -> list[str]:
+        """Return IDs of other extensions installed alongside this one.
+
+        Sourced from ``ExtensionRegistry`` (``.specify/extensions/.registry``)
+        rather than a directory scan: ``ExtensionManager.remove(...,
+        keep_config=True)`` deliberately preserves the extension directory
+        while dropping the registry entry, so a directory scan would treat
+        that config-only leftover as an installed sibling and keep silently
+        absorbing its ``SPECKIT_<sibling>_*`` env vars into no one. The
+        registry is the source of truth for "installed".
+
+        Returns an empty list if the registry is missing or corrupted
+        (fresh project, ad-hoc test harness) so ``_get_env_config`` degrades
+        to its pre-fix behaviour rather than crashing. ``UnicodeError`` is
+        caught alongside ``OSError`` because ``ExtensionRegistry._load()``
+        opens the file in text mode and only handles ``JSONDecodeError`` /
+        ``FileNotFoundError``, so a registry file with non-UTF-8 bytes would
+        otherwise surface a ``UnicodeDecodeError`` here and break *every*
+        config read instead of degrading gracefully.
+
+        Used by ``_get_env_config`` to detect env vars whose remainder claims
+        a longer, sibling-owned prefix (e.g. ``SPECKIT_GIT_HOOKS_URL`` is
+        owned by ``git-hooks`` when it is co-installed with ``git``).
+        """
+        extensions_dir = self.project_root / ".specify" / "extensions"
+        try:
+            return list(ExtensionRegistry(extensions_dir).keys())
+        except (OSError, UnicodeError):
+            return []
+
     def _get_env_config(self) -> Dict[str, Any]:
         """Get configuration from environment variables.
 
@@ -2756,15 +2786,49 @@ class ConfigManager:
         ext_id_upper = self.extension_id.replace("-", "_").upper()
         prefix = f"SPECKIT_{ext_id_upper}_"
 
+        # Cross-extension prefix collision: because ``_`` doubles as both the
+        # separator between the extension ID and the config path *and* the
+        # substitute for ``-`` inside an extension ID, an env var like
+        # ``SPECKIT_GIT_HOOKS_URL`` begins with *both* the ``SPECKIT_GIT_``
+        # prefix of the ``git`` extension and the ``SPECKIT_GIT_HOOKS_`` prefix
+        # of a co-installed ``git-hooks`` extension. It logically belongs to
+        # the extension whose normalized ID is the longer, more specific match
+        # — otherwise config intended for one extension silently surfaces
+        # inside another and can drive hooks that only inspect
+        # ``config.<field> is set``. Build the list of sibling-owned
+        # remainder-prefixes here so a later env var can be skipped if it
+        # matches one.
+        sibling_prefixes: list[str] = []
+        for sibling_id in self._sibling_extension_ids():
+            if sibling_id == self.extension_id:
+                continue
+            sib_upper = sibling_id.replace("-", "_").upper()
+            # A sibling collides only when its normalized ID *extends* our own
+            # (i.e. starts with ``<US>_``). ``git`` vs ``not-git`` is not a
+            # collision; ``git`` vs ``git-hooks`` is.
+            if sib_upper.startswith(ext_id_upper + "_"):
+                # The portion of the env-var *remainder* the sibling claims,
+                # including the trailing ``_`` so a shorter ID that shares a
+                # non-boundary prefix cannot false-positive (e.g. sibling
+                # ``hook`` would not eat env vars under key ``hooks``).
+                sibling_prefixes.append(sib_upper[len(ext_id_upper) + 1 :] + "_")
+
         for key, value in os.environ.items():
             if not key.startswith(prefix):
                 continue
 
+            remainder = key[len(prefix) :]
+            # Skip when a longer sibling ID claims this var — see the block
+            # above. Keeps ``SPECKIT_GIT_HOOKS_URL`` out of the ``git``
+            # extension's config when ``git-hooks`` is co-installed.
+            if any(remainder.startswith(sp) for sp in sibling_prefixes):
+                continue
+
             # Remove prefix and split into parts. Drop empty components from a
             # malformed name (e.g. ``SPECKIT_<EXT>_`` with no key, or
             # consecutive underscores ``SPECKIT_X__Y``) so we never create an
             # entry under an empty key.
-            config_path = [p for p in key[len(prefix) :].lower().split("_") if p]
+            config_path = [p for p in remainder.lower().split("_") if p]
             if not config_path:
                 continue