Tolerate corrupted entries in multi-item listings with diagnostics instead of aborting

[jon-devlapaz]

Problem

When listing library skillsets with tink skillset list --library, if any single entry in $TINK_HOME/skills/ fails validation (e.g. Skillset tree digest mismatch: /Users/.../.tink/skills/common-skills-skillset), the command immediately fails with exit code 1 and aborts.

As a result:

• Healthy, working library skillsets are completely hidden from the user and agent.
• Automated agents cannot discover available skillsets because one legacy or modified tree aborts the entire query.
• No actionable hint or remedy is suggested for repairing or bypassing the corrupted entry.

Proposed change

1. Make multi-item queries (tink skillset list, tink skill list) resilient to individual item validation failures.
2. In human output, list healthy items and print a diagnostic warning block for failed/corrupted items.
3. In machine output (--json), include an item status (e.g., status: "valid" vs status: "digest_mismatch" with diagnostic details).
4. Provide actionable guidance in the diagnostic (e.g. suggest tink skillset refresh <name> or removing the invalid directory).

Acceptance

• tink skillset list --library does not abort when one entry has a digest mismatch.
• Healthy skillsets are listed successfully.
• Corrupted entries are reported with clear diagnostic warning output.
• Exit code distinguishes partial success with warnings from total failure.