Claude's check_ready.creds_file disagrees across the three registry sources

[zomux]

Surfaced during review of #630 (merged), which deliberately did not touch it.

Claude's readiness evidence says three different things depending on which copy is read:

source	creds_file	creds_key
sdk/src/openagents/registry/claude.yaml	~/.claude/.credentials.json	claudeAiOauth
registry/claude.json	~/.claude/sessions	(none)
packages/agent-connector/registry.json	~/.claude/sessions	(none)

Both variants work after #630 (the directory path used to crash the Python loader; now it counts when non-empty), but they check different things — and if Claude Code has moved its credentials the way the Gemini CLI did (to the OS keychain, deleting the on-disk file — the exact failure #630 fixed for Gemini), the .credentials.json variant may be silently stale.

To resolve:

1. Check where current Claude Code builds actually persist subscription credentials (file vs keychain, per-platform).
2. Pick one evidence source and align all three copies (plus workspace/backend/registry/claude.json via sync_registry.py).
3. Remember the connector's registry.json is hand-maintained — the generator would drop drifted blocks (see the note in the package README and fix(core): creds_file readiness — Gemini's evidence moved, Hermes' never parsed, Python's never ran #630's description).

Related pre-existing wart, also from #630's description: _simple_yaml_parse (the PyYAML-absent fallback in loader.py) cannot parse the registry YAML it is the fallback for (install comes back as a list, check_ready as None → AttributeError at import). Worth folding into the same cleanup or splitting out.

[linear]

OADEV-95