test: cover full printed output of opkssh inspect. Closes #356

[fdcastel]

The opkssh inspect unit tests previously checked the underlying data using require.Contains on a few substrings, but did not verify the actual printed output. This PR enhances the tests to cover the complete output format, catching formatting, indentation, and ordering regressions.

Closes #356

Changes

commands/inspect_test.go — test-only changes, no production code modified.

TestInspectKey

• Replaced require.Contains checks with require.Equal against the exact expected output (header, type, fingerprint, and marshal lines).
• Expected fingerprint and marshal prefix are computed from the test key so the assertion is self-contained and deterministic.

TestInspectSSHCert

• Section ordering: Verifies all four section headers (SSH Certificate Information, PKToken Structure, Signature Information, Token Metadata) appear in the correct order.
• Certificate fields: Verifies lines 0–8 of the output by exact index, checking the format and values of Serial, Type, Key ID, Principals, Valid After, Valid Before, Critical Options, and the Extensions header.
• Extensions: Collects all extension lines, sorts them (to handle non-deterministic Go map iteration), and verifies the exact set of six expected extensions with their formatting.
• PKToken payload: Verifies the payload JSON contains expected claims (email, iss, sub, aud).
• Signature information: Verifies both Provider (OP) and Client (CIC) signatures are printed with their algorithm headers.
• Token metadata: Verifies all six metadata fields (Issuer, Audience, Subject, Identity, Token Hash, Provider Algorithm) are printed with the correct label format.

Test helpers added

• requireLineEquals — asserts an exact line match at a given index.
• requireLineMatches — asserts a regex match at a given line index.
• requireLineInSection — asserts at least one line in a section matches a regex.