Improve agent log parsing

[gjkim42]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Improves agent log parsing for OpenCode JSON streams that emit nested step, tool, and token events. kelos logs now shows OpenCode step boundaries, tool summaries, usage, truncation, and non-zero exits without dumping full tool output.

This also updates reporting progress/activity and result capture so nested OpenCode text is recognized, and Gemini capture accepts total token stats.

Which issue(s) this PR is related to:

N/A

Special notes for your reviewer:

Validation:

• make test
• make verify
• git diff --check

Does this PR introduce a user-facing change?

Improve agent log parsing for OpenCode JSON streams so kelos logs, progress/activity reporting, and captured task responses handle nested OpenCode events.

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Summary by cubic

Improves agent log parsing for OpenCode JSON streams. kelos logs now shows clear step boundaries, concise tool summaries, and usage stats without dumping noisy tool output; progress/activity and captured responses handle nested OpenCode text, and Gemini usage accepts total token stats.

• New Features
  • Print numbered step boundaries (“--- Step N ---”) for OpenCode runs.
  • Summarize tool_use events (bash/shell, read/write/edit, grep/glob, webfetch, websearch), include non‑zero exit and truncated, and suppress full tool output.
  • Emit [usage] on step_finish with input, cached, output, plus reasoning, cache_write, and total when present.
  • Parse nested OpenCode text for progress/activity and final response capture; accept Gemini totalInputTokens and totalOutputTokens in usage extraction.

^{Written for commit 76da819. Summary will update on new commits.}