codesign resolves signing identities through the user keychain search
list (first match wins) and ignores --keychain for the lookup. This
runner hosts another project (Sybil-2) whose keychain holds the same
Apple Distribution identity, so if that keychain is locked and appears
earlier in the search list, codesign fails with errSecInternalComponent
no matter how correctly our own keychain is set up. Prepend the fresh
CI keychain to the search list for the build and always delete it
afterward, which restores the original list.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
