Store per-page paragraph indices in section cache to enable precise
XPath-to-page and page-to-XPath mapping without reparsing XHTML.
Forward path (upload): generates XPath directly from paragraph LUT
instead of byte-offset estimation, eliminating drift in chapters
with non-uniform content density.
Reverse path (download): resolves incoming KOReader XPath p[N] to
the exact page via paragraph LUT lookup.
Paragraph counter counts all <p> elements including display:none
to match ChapterXPathIndexer and crengine's standard XPath counting.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
### Summary
This PR introduces a lightweight contributor onboarding docs section
under `docs/contributing/` and improves local formatting ergonomics for
first-time contributors.
The goal is to make CrossPoint easier to contribute to for software
developers who are new to embedded systems (like me), while keeping
onboarding modular and aligned with existing project docs.
### What changed
- Added contributor docs hub: `docs/contributing/README.md`
- Added focused onboarding pages:
- `docs/contributing/getting-started.md`
- `docs/contributing/architecture.md`
- `docs/contributing/development-workflow.md`
- `docs/contributing/testing-debugging.md`
- Linked contributor docs from `README.md` for discoverability
- Expanded architecture documentation with Mermaid diagrams
- Improved `bin/clang-format-fix`:
- prefers `clang-format-21` when available
- validates formatter version and fails fast with a clear message if too
old
- handles missing positional arg safely
- Updated docs to explain common `clang-format` setup/version issues and
install paths (including fallback steps when `clang-format-21` is
unavailable in default apt sources)
### Why
- There was no dedicated contributor onboarding path; first-time
contributors had to infer workflow from multiple files.
- New contributors (especially from non-embedded backgrounds) need a
clear mental model of architecture, runtime flow, and debugging process.
- Local formatting setup caused avoidable friction due to clang-format
version mismatch (`.clang-format` expects newer keys used in CI).
- The updates make contribution setup more predictable, reduce
onboarding confusion, and align local checks with CI expectations.
### Additional context
- No firmware behavior/runtime logic was changed; this PR focuses on
contributor experience and tooling clarity.
---
### AI Usage
> Did you use AI tools to help write this code?
Yes, I used AI tools to assist with generating the documentation. I then
manually reviewed, tested, and refined the code to ensure it works
correctly. please feel free to point out any discrepancies or areas for
improvement.
