docs(bf-2pw): record emitter verification - already complete in bfb50da

notes/bf-2pw.md

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+# Bead bf-2pw: Emitter Implementation Verification
+
+## Status: Already Complete
+
+The `src/emitter.rs` module was fully implemented in commit `bfb50da` ("Add Phase 8: Emitter — text/json/stream-json output formats").
+
+## Verification Results
+
+### Implementation Completeness
+
+All required functionality is present:
+
+1. **Text format** (`OutputFormat::Text`)
+   - Simple text output with trailing newline
+   - Error messages to stderr
+
+2. **JSON format** (`OutputFormat::Json`)
+   - Structured JSON output with all required fields:
+     - `type`: "result"
+     - `subtype`: "success" or error subtype
+     - `is_error`: boolean
+     - `result`: response text (success) or `error_message` (error)
+     - `session_id`: session identifier
+     - `num_turns`: turn count
+     - `duration_ms`: wall-clock duration
+     - `cost_usd`: cost in USD (currently 0)
+     - `claude_version`: Claude version string
+     - `usage`: token usage object with:
+       - `input_tokens`
+       - `output_tokens`
+       - `cache_creation_input_tokens`
+       - `cache_read_input_tokens`
+
+3. **Stream-JSON format** (`OutputFormat::StreamJson`)
+   - Reader thread spawns via `spawn_stream_json_reader()`
+   - Streams JSONL from transcript file
+   - Graceful drain-and-exit on success
+   - Immediate exit on disconnect
+
+### Exit Code Reporting
+
+Exit codes are properly defined in `src/error.rs`:
+- `0`: Success
+- `1`: Assistant error
+- `2`: Internal error
+- `124`: Timeout
+- `130`: Interrupted (SIGINT)
+
+### Test Coverage
+
+All 13 tests pass:
+- Text format correctness
+- JSON format validation
+- Error handling (text and JSON)
+- Stream-JSON streaming
+- Zero token counts
+- Exit codes and subtypes
+
+## Conclusion
+
+No implementation work was needed. The emitter module is complete and all tests pass.