* fix(orcad): seal integration credentials on the headless server instead of storing them in plaintext
The Node SecretStore always reported encryption unavailable, so every
credential writer on orcad fell back to plaintext. orcad now seals with
AES-256-GCM using a host-owned master key kept in the OS keyring (macOS
Keychain, Linux Secret Service) when reachable at first start, else in a
0600 profile file bound to the machine ID. A key that cannot load fails
closed instead of downgrading. Existing plaintext credentials are sealed
on startup without loss.
* docs: describe how the headless server seals credentials and its limits
* fix(orcad): unique credential staging files, no keyring items for temp profiles, isolate startup test
* fix(orcad): keep the credential key with the credentials, one record per machine
* fix(orcad): never re-key over an unreadable record, serialize first-start key creation, refuse an unrestricted key file
* fix(orcad): verify a key record's Windows ACL and wait out a concurrent first start's keyring write
* fix(orcad): keep a keyring claim and fail closed when its store result is uncertain
* fix(credentials): restrict the staged file's Windows ACL before it replaces a credential
* fix(orcad): a temporary profile never creates a key in, or re-seals, the real credential home
* ci: baseline the two single-file credential ACL restrictions
* fix(credentials): stage Windows credentials born restricted and verify the key record asynchronously; document rollback
* test(bitbucket): inject the write failure into the Windows staging writer too
Neil
