Better MP4 re-save; --inject option for day-to-day

[balparda]

No description provided.

[Copilot]

Pull request overview

Adds an --inject/--no-inject CLI flag to control whether animation outputs are post-processed to embed the final animation hash in metadata, and optimizes MP4 metadata rewriting by switching to a lossless ffmpeg re-mux approach.

Changes:

• Introduce --inject/--no-inject for tranz zoom auto, thread it through CLI → render pipeline, and update docs/examples accordingly.
• Rewrite MP4 metadata “rewrite” path to use ffmpeg stream-copy re-muxing instead of re-encoding.
• Update integration tests/scripts and bump version/dependencies/changelog for the 2.1.0 release.

Reviewed changes

Copilot reviewed 13 out of 16 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
tranz.md	Updates generated CLI help to include --inject/--no-inject.
tests_integration/test_installed_cli.py	Uses --inject in animated seahorse integration test.
tests_integration/test_cython_equivalence.py	Uses --inject in multiple equivalence integration tests.
src/tranzoom/core/zoom.py	Rewrites MP4 metadata rewrite to use ffmpeg re-mux (stream copy).
src/tranzoom/core/pixels.py	Tightens MP4/GIF metadata hash handling (strip/empty handling + logging).
src/tranzoom/cli/zoomcommand.py	Plumbs --inject option into ProduceFractalAnimation(...).
src/tranzoom/cli/base.py	Adds new option definition + implements inject/no-inject behavior in animation pipeline.
src/tranzoom/init.py	Bumps package version to 2.1.0.
scripts/make_test_images.sh	Adds --inject to regenerated test animation commands.
requirements.txt	Bumps llama-cpp-python pin to 0.3.31.
README.md	Documents --inject and updates example output text.
pyproject.toml	Bumps project version to 2.1.0.
poetry.lock	Updates lockfile for llama-cpp-python 0.3.31.
CHANGELOG.md	Adds 2.1.0 release notes.
.vscode/settings.json	Adds spellchecker dictionary words (“muxed”, “muxing”).

[BellaKeri]

LGTM, great job