feat(transcript-fixer): add timestamp repair and section splitting scripts

New scripts:
- fix_transcript_timestamps.py: Repair malformed timestamps (HH:MM:SS format)
- split_transcript_sections.py: Split transcript by keywords and rebase timestamps
- Automated tests for both scripts

Features:
- Timestamp validation and repair (handle missing colons, invalid ranges)
- Section splitting with custom names
- Rebase timestamps to 00:00:00 for each section
- Preserve speaker format and content integrity
- In-place editing with backup

Documentation updates:
- Add usage examples to SKILL.md
- Clarify dictionary iteration workflow (save stable patterns only)
- Update workflow guides with new script references
- Add script parameter documentation

Use cases:
- Fix ASR output with broken timestamps
- Split long meetings into focused sections
- Prepare sections for independent processing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

transcript-fixer/references/workflow_guide.md

@@ -17,6 +17,7 @@ Detailed step-by-step workflows for transcript correction and management.
   - [5. Stage-by-Stage Execution](#5-stage-by-stage-execution)
   - [6. Context-Aware Rules](#6-context-aware-rules)
   - [7. Diff Report Generation](#7-diff-report-generation)
+  - [8. Workshop Transcript Split + Timestamp Rebase](#8-workshop-transcript-split--timestamp-rebase)
 - [Batch Processing](#batch-processing)
   - [Process Multiple Files](#process-multiple-files)
   - [Parallel Processing](#parallel-processing)
@@ -400,6 +401,30 @@ See `file_formats.md` for context_rules schema.
 
 See `script_parameters.md` for advanced diff options.
 
+### 8. Workshop Transcript Split + Timestamp Rebase
+
+**Goal**: Split a long workshop transcript into sections such as setup chat, class, and debrief, then make each section start from `00:00:00`.
+
+**Steps**:
+
+1. **Correct transcript text first** (dictionary + AI/manual review)
+2. **Pick marker phrases** for each section boundary
+3. **Split and rebase**:
+
+```bash
+uv run scripts/split_transcript_sections.py workshop.txt \
+  --first-section-name "课前聊天" \
+  --section "正式上课::好，无缝切换嘛。对。那个曹总连上了吗？那个网页。" \
+  --section "课后复盘::我们复盘一下。" \
+  --rebase-to-zero
+```
+
+4. **If you already split the files**, rebase a single file directly:
+
+```bash
+uv run scripts/fix_transcript_timestamps.py class.txt --in-place --rebase-to-zero
+```
+
 ## Batch Processing
 
 ### Process Multiple Files