feat(cli): report distinct exit codes for benchmark, auth and upload failures

[akx]

In a downstream project using codspeed-action, we were wondering if it would be possible to make the action pass when only uploading/auth failed (e.g. since a fork doesn't have CodSpeed enabled).

I looked at codspeed-action, and there wasn't an obvious way to do that (aside from capturing the runner output and grepping it for a human-readable error string, yeugh), so here's a PR that adds a handful of exit codes to the runner.

If this gets merged, the follow-up in the action is to add an input for ignoring error codes 4 and 5.

[greptile-apps]

Greptile Summary

This PR introduces typed CLI failure markers and maps benchmark, authentication, and upload errors to distinct process exit codes for downstream automation.

• Adds the public exit-code definitions, help text, error wrappers, and top-level process mapping.
• Classifies selected benchmark process failures across memory, wall-time, and Valgrind execution.
• Classifies selected authentication and upload failures while preserving nested authentication markers.

Confidence Score: 3/5

The PR should not merge until authentication coverage and tracker/profiler status classification match the documented exit-code meanings.

Reachable authentication failures still return the generic status, while independent memory-tracker and wall-time-profiler failures are incorrectly reported as failures of the benchmark command itself.

Files Needing Attention: src/executor/orchestrator.rs, src/executor/memory/executor.rs, src/executor/wall_time/executor.rs

Important Files Changed

Filename	Overview
src/exit_code.rs	Defines the new marked-error mechanism, public exit-code contract, help text, and chain-preserving classification.
src/executor/orchestrator.rs	Adds upload and token-refresh classification, but earlier provider authentication failures remain generic.
src/executor/memory/executor.rs	Classifies the memtrack process status as a benchmark failure even when the tracker itself fails.
src/executor/wall_time/executor.rs	Classifies profiler process failures as benchmark failures because the workload status is not captured separately.
src/executor/valgrind/measure.rs	Correctly distinguishes the Valgrind tool status from the benchmark command's separately recorded status.
src/upload/uploader.rs	Marks unauthorized upload-target responses as authentication failures while leaving other upload errors for the enclosing upload marker.
src/main.rs	Converts classified anyhow error chains into the corresponding process exit status after logger cleanup.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    CLI[run or exec] --> Init[Initialize environment provider]
    Init --> Execute[Execute benchmark]
    Execute --> Upload[Upload completed results]
    Init -->|auth error| Generic[Generic exit 1]
    Execute -->|outer process nonzero| Benchmark[Benchmark exit 3]
    Upload -->|auth error| Auth[Auth exit 4]
    Upload -->|other error| UploadCode[Upload exit 5]

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Prompt To Fix All With AI

### Issue 1
src/executor/orchestrator.rs:274-277
**Authentication classification starts too late**

When provider initialization rejects missing CI credentials or local repository fallback encounters an expired token, the failure occurs before this marked token-refresh call and exits with generic code 1 instead of the documented authentication code 4. Downstream automation therefore cannot reliably distinguish and optionally ignore these authentication failures.

### Issue 2
src/executor/memory/executor.rs:191-195
**Tracker failures mimic benchmark failures**

When memtrack fails to load or finish tracking, its ring buffer overflows, or a wall-time profiler fails independently, these checks pass the outer tool process status to `benchmark_failed`. The CLI consequently returns code 3 even when the benchmark succeeded, causing downstream automation to apply benchmark-failure policy to a measurement-tool failure.

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For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(cli): report distinct exit codes fo..." | Re-trigger Greptile}