docs: restructure README, combined feature section, and local PDF build

[charlesangus]

Documentation-only work (plus two setObjectName additions the panel screenshots depend on).

README restructure

• Features reordered, led by a new Regular Knob Readout section.
• Channels / Masks / Merges / Mix folded into a single Channels, Masks, Merges and Mix section with one combined screenshot.
• Node Class + File Readout gathered into an Other Readouts section, placed just before the de-overlap features.
• Note that De-overlap All is handy the first time you open a script after enabling Labelmaker.
• Configuration: dropped the Config Cascade and Environment Variables subsections; Preferences is now a subsection of Configuration.

User Guide PDF

• Intro gets its own Introduction section after the table of contents.
• Body starts on a fresh page after the ToC.
• Stronger widow/orphan protection — a heading is never stranded at a page foot (needspace guarded with \if@nobreak so a section heading stays with an immediately-following subsection).

PDF build moved local + committed

The GitHub-hosted ubuntu-24.04 runner ships neither pandoc/TeX Live nor Nuke, so installing the TeX Live toolchain on every release was slow and heavy. The PDF and screenshots are now built locally and committed; CI no longer builds any docs — it only bundles the committed docs/user-guide.pdf and docs/images/*.png into the release zip.

• Suppress pandoc's spurious \usepackage{lmodern} under xelatex so make pdf builds with no extra TeX dependency.
• Regenerated the DAG screenshots for the new layout; removed the now-orphaned PNGs.
• CLAUDE.md updated to document the local-build-and-commit flow.

Verification

• ruff check . clean, pytest tests/ — 62 passed.
• make pdf builds cleanly (no stub, no lmodern); every page reviewed — correct section order, no lone headings, images anchored beside their text.

[Copilot]

Pull request overview

This PR updates Labelmaker’s documentation to make the README the single source of truth, adds a locally-built (and committed) User Guide PDF pipeline, and refreshes the committed screenshots/PDF assets used in releases (plus two setObjectName additions to support deterministic panel screenshots).

Changes:

• Restructured README.md feature sections and switched screenshots to repo-relative docs/images/*.png paths.
• Added a local docs build toolchain (Makefile, pandoc defaults + Lua filter, README→User Guide derivation script) and documented the workflow in CLAUDE.md.
• Updated the release workflow to bundle committed docs/user-guide.pdf and docs/images/*.png instead of generating docs in CI.

Reviewed changes

Copilot reviewed 14 out of 28 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
README.md	Restructures documentation and switches images to docs/images/* relative paths; references committed PDF.
Makefile	Adds local targets to regenerate screenshots and build the committed User Guide PDF.
labelmaker_prefs_dialog.py	Adds setObjectName to support automated panel screenshot targeting.
labelmaker_config_editor.py	Adds setObjectName to support automated panel screenshot targeting.
docs/screenshots/panels.scenarios.json	Defines screenshotter scenarios for capturing Preferences and Config Editor panels.
docs/screenshots/features.nk	Adds the Nuke script used to capture the DAG feature screenshots.
docs/screenshots/build_features_nk.py	Adds a generator script for features.nk to keep screenshots reproducible.
docs/screenshots/bootstrap/menu.py	Adds a clean bootstrap to load Labelmaker and open dialogs non-modally for capture sessions.
docs/pandoc/pdf.yaml	Adds pandoc defaults for consistent PDF generation with the project LaTeX class.
docs/pandoc/float-images.lua	Adds a pandoc Lua filter to anchor images beside text and improve table column wrapping in PDF output.
docs/pandoc/build_user_guide_md.py	Adds README→User Guide Markdown derivation (drops install section, adds title block).
docs/latex/training_doc.cls	Adds/updates the LaTeX class used to style the generated PDF and enforce pagination rules.
docs/images/.gitkeep	Keeps the images directory present in git.
CLAUDE.md	Documents the local-build-and-commit documentation workflow and regeneration commands.
.gitignore	Ignores local tools dir, Nuke autosaves, capture HOME, and intermediate PDF build artifacts.
.github/workflows/release.yml	Updates release packaging to include committed PDF and screenshots rather than building docs in CI.

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[charlesangus]

Fixed in ffad941 — the make pdf header comment now states the PDF is built locally and committed (CI does not build the docs).

[charlesangus]

Fixed in ffad941 — \ProvidesClass is now training_doc, matching the filename and pandoc's documentclass: training_doc, so the requested-vs-provided class warning is gone.