feat(cli): add hyperframes auth OAuth (PKCE + loopback + refresh)

[jrusso1020]

What

Adds OAuth 2.0 + PKCE login as the default for hyperframes auth login,
plus refresh-token + 401 auto-retry + auth refresh. Stacks on top of
PR #1081 (the API-key + shared store work).

• hyperframes auth login (no flags) — opens the user's browser to
  /v1/oauth/authorize, captures the code on an ephemeral
  127.0.0.1:<port>/oauth/callback, exchanges it for tokens with
  PKCE S256, and persists. --api-key opts back into the legacy
  long-lived-key path from PR feat(cli): add hyperframes auth login --api-key, status, logout #1081.
• hyperframes auth refresh — force-refresh the OAuth access token
  using the stored refresh_token. Mostly useful for testing the path.
• hyperframes auth logout — best-effort revokes via
  POST /v1/oauth/revoke (RFC 7009) before wiping local state.
• AuthClient now refreshes-and-retries once on a 401 when the
  caller wires onUnauthenticatedRefresh. auth status wires it.

Internals added in packages/cli/src/auth/:

• pkce.ts — RFC 7636 code_verifier + S256 code_challenge.
• loopback.ts — ephemeral 127.0.0.1 HTTP server; state validation,
  120s timeout, styled success/error page.
• browser.ts — wraps open with a BROWSER=none /
  HF_NO_BROWSER=1 fallback that prints the URL.
• oauth.ts — startAuthorizationCodeFlow, refreshTokens,
  revokeTokens, requireOAuthConfigured, parseTokenResponse.

Why

This is the foundation OAuth flow that lets free-tier users authenticate
without managing a long-lived key. Refresh + auto-retry means CLI
commands keep working past the access_token lifetime without bugging
the user.

The OAuth client_id (q2A2QRSke2LrFTPJhoDbHtXh) is the one James
created in the oauth2_client table. Baked in as a build-time default;
override via HYPERFRAMES_OAUTH_CLIENT_ID for dev/test.

How

• Public client: PKCE only, no client_secret. Backend already
  requires PKCE (movio/logic/oauth2.py:638).
• Loopback port is ephemeral (server.listen(0)) — the backend
  wildcards localhost ports for public clients
  (movio/model/oauth2.py:check_redirect_uri), so the registered
  redirect URI's port is a placeholder.
• State parameter is generated per-flow + validated on callback to
  prevent CSRF.
• Token-response parsing is permissive on expires_in type (some
  servers return it as a string) but strict on access_token presence.
• 401 retry happens at the AuthClient.fetchUser layer, not the
  command layer — so future endpoints inherit it for free.
• persistOAuth merges into the existing store (preserves co-located
  api_key). auth login (API-key path) does the symmetric thing.

Test plan

• 80 unit tests, all green. vitest run src/auth/.
• PKCE: verifier within 43-128 chars, challenge = SHA-256, S256
  method, distinct outputs each call.
• Loopback: state mismatch / IdP error / missing-code / timeout /
  404 non-callback paths all rejected; success path captures code.
• OAuth: refreshTokens posts correct body, persists, throws
  REFRESH_FAILED on 400/401 and API_ERROR on 5xx. Existing
  api_key preserved on refresh.
• AuthClient: 401 retries with refreshed bearer on OAuth, does
  NOT retry for api_key, returns 401 if refresh hook fails.
• bunx oxlint / bunx oxfmt --check / bunx tsc clean.
• bunx fallow audit --base origin/main --fail-on-issues — only
  inherited help.ts:showUsage finding (from main, not this PR).
• Smoke test against dev API:
  HEYGEN_API_URL=https://api.dev.heygen.com hyperframes auth login
  then hyperframes auth status then hyperframes auth refresh.

Out of scope

• Cloud render commands — separate plan.
• PR 4 (heygen-cli read-side JSON support) — independent, ships after.

[jrusso1020]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(cli): add hyperframes auth OAuth (PKCE + loopback + refresh) #1084 👈 (View in Graphite)
• feat(cli): add hyperframes auth login --api-key, status, logout #1081
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[jrusso1020]

Self-review pass on the OAuth work — addressed 12 of 15 findings. Force-push above includes the fixes.

Fixed (high severity):

1. persistOAuth wiped refresh_token on no-rotation refresh — RFC 6749 §6 lets the server omit refresh_token in a refresh response, and we were silently dropping the previous one. Now merges the new tokens into the existing oauth block. New test covers this.
2. redirectUri was rebuilt from req.socket.localAddress — could drift on dual-stack hosts and fail the byte-identical match at /v1/oauth/token. Now the loopback passes the original redirectUri (captured once from server.address().port) through to the token-exchange callsite.
3. refresh.ts double-persisted with a stale snapshot — dropped the second writeStore; refreshTokens already persists via persistOAuth with merge semantics.
4. revokeTokens had no timeout — added AbortController with 5s default. A flaky network can no longer hang logout for the OS-level TCP timeout.
5. revokeTokens ignored response status and only revoked one token — now logs HTTP ≥400 to stderr; logout revokes both refresh_token and access_token with the proper RFC 7009 token_type_hint.

Fixed (medium severity):
6. expires_in ≤ 0 → immediate-refresh loop — clamped to a 30s minimum.
7. parseTokenResponse threw ErrApi(200, …) for shape failures (self-contradictory message, wrong routing through tryRefresh). Now throws ErrRefreshFailed so callers consistently route to "log in again".
8. OAuth access_token / refresh_token not isHeaderSafe-validated — added the same isHeaderSafe check used by the store's JSON read path, so an IdP can't smuggle CRLF into headers via the token-exchange response.
9. runOAuthLogin no rollback on verify failure — wired the same refresh hook as auth status so a transient 401 right after sign-in transparently refreshes-and-retries; verify failure now downgraded to a warning (tokens are valid on disk, force-rolling-back would be worse).
10. revokeTokens called resolveClientId() outside the try — now returns silently when OAuth isn't configured. Best-effort contract holds for any caller.
11. State leaked in console.log of authorize URL — now logs origin + pathname only; the random state stays out of scrollback / CI logs.
12. state !== expectedState — replaced with crypto.timingSafeEqual. Low real risk on loopback but a gratuitous deviation. Also added GET-only method check on the loopback handler.
13. requireOAuthConfigured() exited inline — renamed and split: assertOAuthConfiguredOrExit() (command-entry helper that exits) vs resolveClientId() (throws). Pattern matches the rest of the file.
14. Dynamic-import of same module already statically imported — removed.

Deferred (won't fix in this PR):

• HEYGEN_API_URL accepts arbitrary hosts — flagged in the prior review too. By design today for dev testing (api.dev.heygen.com), and removing it would block that workflow. Reasonable follow-up: warn on stderr when the URL is non-default, and possibly require --allow-insecure-base-url for non-HTTPS schemes. Tracked separately.
• process.exit after console.error can drop stderr when piped — would need to await stderr drain across every call site. Real but small-impact; deferring to a focused follow-up.

Tests: 89 unit tests, all green. Lint/format/typecheck/fallow clean.