fix(cli): suppress library warning noise in tracker audit / run listing / tracker diagnose

[Copilot]

Phase 2 library extraction introduced new non-fatal stderr warnings from library internals that now leak into user-facing CLI commands (tracker audit/listing and tracker diagnose) on stale or corrupted run artifacts. This restores prior CLI UX while keeping library-level warning surfacing configurable for non-CLI consumers.

• Library API: configurable warning sink

  • Added ListRunsWithConfig(workdir, ListRunsConfig) with ListRunsConfig.LogWriter.
  • Added DiagnoseWithConfig(runDir, DiagnoseConfig) and DiagnoseMostRecentWithConfig(workdir, DiagnoseConfig) with DiagnoseConfig.LogWriter.
  • Existing entry points (ListRuns, Diagnose, DiagnoseMostRecent) remain, defaulting nil writer to os.Stderr to preserve library behavior.

• CLI: explicit suppression for user-facing commands

  • cmd/tracker/audit.go now calls ListRunsWithConfig(..., LogWriter: io.Discard).
  • cmd/tracker/diagnose.go now calls DiagnoseWithConfig / DiagnoseMostRecentWithConfig with LogWriter: io.Discard.
  • Result: non-fatal parsing/read warnings no longer appear as CLI stderr noise.

• Regression coverage

  • Added focused tests to verify:
    • library warning emission through custom writers
    • CLI stderr suppression when artifact files are unreadable/malformed but processing continues

• Docs

  • Updated CHANGELOG.md (Unreleased / Fixed) to reflect CLI warning suppression and new configurable log-writer behavior.

// CLI path: suppress non-fatal library warnings for end users.
report, err := tracker.DiagnoseWithConfig(runDir, tracker.DiagnoseConfig{
    LogWriter: io.Discard,
})

[Copilot]

Pull request overview

This PR restores prior CLI UX by suppressing non-fatal library-originated warning output on stderr for user-facing commands (tracker audit run listing and tracker diagnose), while keeping the library’s default warning behavior and making the warning sink configurable for non-CLI consumers.

Changes:

• Added ListRunsWithConfig/ListRunsConfig{LogWriter} and DiagnoseWithConfig/DiagnoseMostRecentWithConfig/DiagnoseConfig{LogWriter} to route non-fatal warnings to a configurable io.Writer (defaulting to os.Stderr).
• Updated CLI commands to pass io.Discard so library warnings don’t leak into CLI stderr.
• Added regression tests covering library warning routing and CLI stderr suppression; updated changelog.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tracker_audit.go	Introduces ListRunsWithConfig + ListRunsConfig.LogWriter and routes listing warnings through the configured writer.
tracker_diagnose.go	Introduces DiagnoseWithConfig/DiagnoseMostRecentWithConfig + DiagnoseConfig.LogWriter and routes malformed status.json warnings through the configured writer.
tracker_audit_test.go	Adds a focused unit test verifying warnings are emitted via a custom writer when activity log is unreadable.
tracker_diagnose_test.go	Adds a focused unit test verifying warnings are emitted via a custom writer when status.json is malformed.
cmd/tracker/audit.go	Switches run listing to ListRunsWithConfig(..., LogWriter: io.Discard) to suppress stderr noise.
cmd/tracker/diagnose.go	Switches diagnose paths to DiagnoseWithConfig / DiagnoseMostRecentWithConfig with io.Discard.
cmd/tracker/audit_test.go	Adds an integration-style test ensuring listing still works and library warnings are suppressed on stderr.
cmd/tracker/diagnose_test.go	Adds an integration-style test ensuring diagnose still prints output and suppresses library warnings on stderr.
CHANGELOG.md	Documents the CLI warning suppression and new configurable log-writer behavior.

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[clintecker]

Superseded by merged #113, which added AuditConfig.LogWriter and DiagnoseConfig.LogWriter (nil → io.Discard), and the CLI (cmd/tracker/audit.go, cmd/tracker/diagnose.go) now passes io.Discard to silence library warnings for user-facing commands. Closes issue #104 via #113.