Add VHS timing sync command and optional pipeline integration

[jmjava]

Summary

This PR contains the VHS timing sync bundle:

• Feature: sync VHS tape Sleep durations from timing.json (Whisper) #11 docgen sync-vhs command to rewrite tape Sleep durations from timing.json
• Feature: optional tape-sync step in generate-all / rebuild-after-audio after timestamps #14 optional integration in the pipeline immediately after timestamps

It also includes a follow-up merge-resolution commit after syncing with latest origin/main.

What changed

New command: docgen sync-vhs

Added src/docgen/tape_sync.py and new CLI command:

docgen sync-vhs [--segment 01] [--dry-run]

Behavior:

• loads animations/timing.json
• maps each VHS segment/tape to timing data by segment name/id/tape stem
• parses .tape files for Type -> Enter -> Sleep blocks after the first Show
• divides timing duration into equal windows per block
• computes new Sleep using:
  • typing estimate: len(typed_text) * typing_ms_per_char
  • cap: max_typing_sec
  • floor: min_sleep_sec
• rewrites tape files unless --dry-run is set

Optional pipeline integration after timestamps

Pipeline now optionally runs VHS tape sync immediately after timestamps:

• enabled when either config is true:
  • pipeline.sync_vhs_after_timestamps
  • vhs.sync_from_timing
• new CLI flag to suppress mutation on a run:
  • docgen generate-all --skip-tape-sync

Config additions

Added in Config:

• pipeline.sync_vhs_after_timestamps (default false)
• vhs.sync_from_timing (default false)
• vhs.typing_ms_per_char (default 45)
• vhs.max_typing_sec (default 2.5)
• vhs.min_sleep_sec (default 0.1)

Scaffolding/docs updates

• docgen init now writes sync options into generated config.
• README updated with:
  • docgen sync-vhs command
  • generate-all --skip-tape-sync
  • sync configuration examples
• docs/demos/docgen.yaml updated with example sync settings.

Merge conflict resolution with latest main

After fetching and merging origin/main, conflicts were found in:

• README.md
• docs/demos/docgen.yaml
• src/docgen/config.py
• src/docgen/init.py
• tests/test_config.py

Classification:

• All were simple content merges (additive docs/config/test changes).
• No conflicting product intent or incompatible behavioral direction detected.

Resolution approach:

• preserved both upstream pipeline-correctness docs and sync-vhs docs in README
• kept upstream defaults plus new sync config accessors in Config
• retained sync scaffolding in init where appropriate
• kept extended config assertions in tests

Tests

Added:

• tests/test_tape_sync.py

Updated:

• tests/test_config.py for new sync config accessors

Verification

• python3 -m pytest tests -q --ignore=tests/e2e -> 84 passed
• python3 -m ruff check src tests -> All checks passed

Issue linkage

Closes #11
Closes #14