Merge Main into Belt Printer

Merge origin/main (00429da739) into belt-printer.

Conflicts resolved:
- src/CMakeLists.txt: keep both wxInspector workarounds.
- GCodeProcessor.cpp: keep the belt compare_pos / z_for_height lines.
- PrintObjectSlice.cpp: the belt bbox-Z guard also covers main's
  printable_region_ids bookkeeping.
- TreeSupport.cpp: the belt-floor check runs before main's PendingNode
  queueing.
- Tab.hpp: keep the belt fields, drop the removed upload description
  fields.
- tests/libslic3r/CMakeLists.txt: keep both test files.

Also included:
- eSUN PLA belt presets declare their own filament_id (OFkrxQC4) and
  scripts/filament_id_snapshot.json is regenerated, as main's filament_id
  check requires.
- Custom.json version bumped to 02.04.00.05 so the belt entries reach
  existing installs.
- Fix the ambiguous WithinRel call in the belt apron width test, which
  otherwise breaks the fff_print build.

AGENTS.md

@@ -30,6 +30,13 @@ ctest --test-dir ./tests/libslic3r              # individual suite
 ctest --test-dir ./tests/fff_print
 ```
 
+## Documentation
+
+- Docs live in `docs/`; the high-level design of a subsystem goes in `docs/HLSD/<subsystem>.md`.
+- Describe the design as it stands — what the subsystem does, why it exists, and the constraints that shape it. Not the route that got there: no phases, task lists, status markers, or "before/after this PR" framing.
+- Planning and investigation output (brainstorms, superpowers design and plan docs) stays in `docs/superpowers/`, which is gitignored. Never commit it.
+- Write a doc only when the design is not evident from the code, and when a change invalidates an existing one, update it in the same PR.
+
 ## Code Style
 
 - C++17, selective C++20. PascalCase classes, snake_case functions/variables