fix(tools): importers clear the read-only LFS bit before saving; docs refresh

0.1.3 packaging and setup fixes from what 0.1.x actually exposed.

- New Tools/ue_common.py: make_writable() clears the read-only bit an LFS .umap
  checks out with (save_map() otherwise returns False silently and the staged actor
  is lost) and require_saved() makes that failure visible. ue_hero_facade_import and
  ue_import_north_buildings now call it; the map builders already did. Verified from
  a forced 0o444 map: chmod logged, save_map True, exit 0.
- Docs/build.md: pipeline table now lists the seven site FBXs plus frontage, north,
  hero and map steps and the shared FBX preset; packaging archive corrected to
  Builds/GigLineQA; packaged-log location and -qaselftest usage documented; new
  'Traps that cost real time in 0.1.x' table (read-only save, hero --out is the FBX,
  MPFB add-on path, shot actor quitting under QA, null-RHI trace trap).
- Docs/setup.md: fresh-checkout build marked verified 2026-11-08 and the blocker
  closed; new optional-keys section for OPENROUTER_API_KEY and MAPBOX_ACCESS_TOKEN
  (gitignored .env, not needed by build/tests/release).
- Docs/Architecture 07 + architecture.md: build-output path corrected, marked
  outside the repository.
- 5 new tests for ue_common (54 total).

TODO.md

@@ -13,10 +13,10 @@ Actionable task list for this project. This file is the single, central place fo
 
 Suggested blender skills: **export-pipeline** and **unreal-export** (scale/pivot/normals/materials/collision verification) if any packaging defect traces back to the Blender export presets.
 
-### Patch tasks
+### Patch tasks - active - 01a1b26b-3c94-707f-9665-2f6b4a79b564 (branch `packaging-setup-0.1.3`)
 
-- [ ] Fix any packaging or build issues encountered in `0.1.x`.
-- [ ] Update `Docs/` setup instructions for anything that changed.
+- [x] Fix any packaging or build issues encountered in `0.1.x`. **Done 2026-11-09.** New `Tools/ue_common.py`: `make_writable()` clears the read-only bit an LFS `.umap` checks out with, and `require_saved()` turns a silent `save_map(False)` into a logged failure. `ue_hero_facade_import.py` and `ue_import_north_buildings.py` now call it before saving (verified from a forced `0o444` map: chmod note logged, `save_map: True`, exit 0); the map builders already did. `Docs/build.md` also gained the current pipeline table (7 site FBXs, frontage, north, hero, map), the archive path `Builds/GigLineQA`, the packaged-log location, the `-qaselftest` usage, and a **traps** table covering the read-only save, the hero `--out`-is-FBX mistake, the MPFB add-on path, the shot actor quitting under QA, and the null-RHI trace trap.
+- [x] Update `Docs/` setup instructions for anything that changed. **Done 2026-11-09.** `Docs/setup.md`: fresh-checkout build marked verified (2026-11-08) with the blocker closed, plus a new _optional keys_ section (`OPENROUTER_API_KEY`, `MAPBOX_ACCESS_TOKEN`, both from the gitignored `.env`, neither needed by build/tests/release). `Docs/build.md`: header reframed for the demo, packaging command and archive corrected to `Builds/GigLineQA`, packaged-log path documented. `Docs/Architecture/07` + `architecture.md`: build-output path corrected and marked outside the repo.
 - [ ] Tag `v0.1.3` and write `CHANGELOG.md` entry; then remove this section.
 
 ## 0.1.4 — Proper building façades (patch)