docs: record spike 2 results, add spike 1/3 manual scripts
Spike 2 (data source) completed:
- All SQLite threads fields verified stable (model, cwd, git_branch, tokens_used)
- JSONL event names stable across 2 sessions (function_call, task_started, token_count, etc.)
- Bonus: token_count event has rate_limits.primary/secondary.used_percent and plan_type
- HudState updated with rateLimitPrimary, rateLimitSecondary, planType fields
Spike 1 (pane mode): pending - tmux not installed, manual steps documented
Spike 3 (inline): pending - needs real TTY, test script provided
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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