The Keys page only rendered env vars present in a catalog (OPTIONAL_ENV_VARS
or the provider catalog); any other key a user set in .env was invisible, and
there was no way to add an arbitrary env var from the GUI (e.g. to inject a
var a skill or MCP server needs).
Backend: GET /api/env now also emits a row for every on-disk .env key that
isn't in any catalog, flagged category="custom" + custom=true and
password-masked (an unrecognised key could hold anything, so it's redacted and
reveal-gated like any secret). Channel-managed credentials stay excluded. The
write (PUT /api/env) and reveal (POST /api/env/reveal) paths already handle
arbitrary keys, with the existing env-name guard + denylist (PATH, LD_PRELOAD,
PYTHONPATH, …) enforced server-side — no new write surface.
Frontend: a new "Custom Keys" section lists those custom rows and carries an
add-a-key form (client-side name validation mirroring the backend regex; the
new row reuses the normal edit/save flow, so on save it round-trips back from
the backend as a durable custom row). i18n added for en + zh + types.
Tests: behavior-contract coverage that an unknown .env key surfaces as a
masked custom row and a catalogued key does not — verified to fail on the
pre-fix backend.
