feat: add Pi session support (v2 subagent dirs + v3 native format)

[adamjramirez]

Summary

Adds support for pi sessions that were previously invisible to Rudel. Closes #153.

Before: 60 sessions visible (Claude Code only)
After: 1,188 sessions visible (Claude Code + Pi v2 + Pi v3)

Two Pi storage formats

Format	Location	Structure	Count
Pi v2	~/.claude/projects/<project>/<uuid>/subagents/agent-*.jsonl	Same JSONL as Claude Code	~282
Pi v3	~/.pi/agent/sessions/--<encoded-cwd>--/<timestamp>_<uuid>.jsonl	Different schema (own event types, different usage field names)	~846

Approach

New PiAdapter following the existing adapter pattern (like Codex):

• Registered via registerScanOnlyAdapter() — shares source: "claude_code" without colliding in the adapter registry. No SourceSchema changes needed.
• v2 sessions: Reads subagent files, concatenates into content field, populates subagents map
• v3 sessions: Transforms pi's native JSONL format into Claude Code-compatible JSONL so the ClickHouse materialized view can extract analytics (timestamps, tokens, model, errors, etc.)

v3 content transformation

The MV parses content line-by-line expecting Claude Code format (type: "user"/"assistant" at line level, message.usage.input_tokens, etc.). Pi v3 uses different structures, so the adapter transforms on upload:

• {type: "message", message: {role: "user"}} → {type: "user", ...}
• Usage: input → input_tokens, output → output_tokens, cacheRead → cache_read_input_tokens, cacheWrite → cache_creation_input_tokens
• Includes uuid and sessionId so the web UI conversation parser works
• Strips v3-only fields (api, provider, stopReason, cost, totalTokens) to reduce content size
• Skips non-interaction lines (session, compaction, thinking_level_change, toolResult)

Changes

File	Change
packages/agent-adapters/src/adapters/pi/index.ts	New — Pi adapter (v2 + v3 scanning, content transform)
packages/agent-adapters/src/registry.ts	registerScanOnlyAdapter() for shared-source adapters
packages/agent-adapters/src/index.ts	Export + register Pi adapter
apps/cli/src/lib/session-resolver.ts	Resolve pi sessions by UUID or path (v2 dirs + v3 files)
apps/cli/src/commands/upload.ts	Route to Pi adapter in all upload paths (interactive, single, retry)
apps/cli/src/commands/dev/list-sessions.ts	Show [Pi] label for pi sessions
apps/cli/src/commands/enable.ts	Handle Pi's no-op hooks gracefully
apps/cli/src/__tests__/agents.test.ts	24 tests covering v2 + v3 discovery, transform, upload

Zero API/schema/migration changes.

Tested

• bun run check-types ✅
• bun run lint ✅
• bun test — 24 pass, 0 fail ✅
• Real uploads of v2 and v3 sessions to app.rudel.ai — sessions appear with correct analytics, timestamps, conversation view ✅

Follow-up suggestion

Currently pi sessions show as source: "claude_code" since we reuse the existing source to avoid schema changes. A natural follow-up would be adding "pi" to SourceSchema so the UI can distinguish which harness produced a session.