Seeding an oauth2-proxy secret by hand means an agent shell-plumbing a
client secret and a cookie secret, which the classifier blocks. seed-oauth
does it in one self-contained invocation: it reads the KV path, fills in
only the keys that are missing, preserves everything else and prints key
names and the new version, never a value.
- Add SeedOAuth in internal/agent: read-modify-write of the client_id,
client_secret and cookie_secret keys with per-key created/kept/rotated
actions and a no-op when nothing changed.
- Generate secrets from 32 crypto/rand bytes; cookie_secret is base64url so
it decodes to exactly the 32 bytes oauth2-proxy requires.
- Add ReadKVOptional (missing secret = empty) and WriteKVAny (non-string
fields survive a round trip) to the KV-v2 client.
- Wire the seed-oauth subcommand and document it in README and AGENTS.md.
- Cover fresh create, patch-preserves-client_secret, other-key
preservation, --rotate, idempotence, denial errors and secret leakage.