docs: remove stale documentation and update for post-ztools architecture

Remove critically stale docs:
- docs/REPOSITORY_STATE.md — snapshot from 2026-01-31, all data outdated
- docs/MULTI_USER_CLIENT.md — duplicate of DAG_CLIENT_INTEGRATION.md
- docs/src/guide/ztools.md — describes removed addon
- docs/KNOWN_ISSUES.md — replaced by Gitea issue tracker

Update docs for ztools removal (#344), gears addition, and KCSDK progress:
- OVERVIEW.md: fix version (v0.1.5), FreeCAD base (1.2.0), submodule table
- ARCHITECTURE.md: replace ztools with gears in bootstrap flow and source layout
- COMPONENTS.md: remove ztools section, add gears, remove stale missing-icons note
- INTEGRATION_PLAN.md: mark Phase 7 #353-#356 as DONE, update Layer 5 diagram
- README.md: update project structure, load order, feature descriptions
- CI_CD.md: add context for disabled macOS/Windows builds (#164)
- SUMMARY.md: remove ztools guide from mdBook navigation

docs/ARCHITECTURE.md

@@ -20,10 +20,7 @@ FreeCAD startup
        │    └─ for each addon in order:
        │         └─ exec(InitGui.py)
        │              ├─ sdk (priority 0):    logs "SDK loaded"
-       │              ├─ ztools (priority 50): schedules deferred _register() (2000ms)
-       │              │    ├─ imports ZTools commands
-       │              │    ├─ installs _ZToolsManipulator (global)
-       │              │    └─ injects commands into editing contexts
+       │              ├─ gears (priority 40): registers GearsWorkbench
        │              └─ silo (priority 60):  registers SiloWorkbench
        │                   └─ schedules deferred Silo overlay registration (2500ms)
        ├─ EditingContextResolver singleton created (MainWindow constructor)
@@ -34,7 +31,6 @@ FreeCAD startup
             ├─  500ms: _register_kc_format()        → .kc file format
             ├─ 1500ms: _register_silo_origin()      → registers Silo FileOrigin
             ├─ 2000ms: _setup_silo_auth_panel()     → "Database Auth" dock
-            ├─ 2000ms: ZTools _register()            → commands + manipulator
             ├─ 2500ms: Silo overlay registration     → "Silo Origin" toolbar overlay
             ├─ 3000ms: _check_silo_first_start()    → settings prompt
             ├─ 4000ms: _setup_silo_activity_panel() → "Database Activity" dock
@@ -65,7 +61,7 @@ The loader (`addon_loader.py`) processes addons in this order:
 5. **Load** — execute `Init.py` (console) then `InitGui.py` (GUI) for each addon
 6. **Register** — populate `FreeCAD.KindredAddons` registry with addon state
 
-Current load order: **sdk** (0) → **ztools** (50) → **silo** (60)
+Current load order: **sdk** (0) → **gears** (40) → **silo** (60)
 
 ## Key source layout
 
@@ -98,14 +94,12 @@ mods/sdk/                    [dir] Kindred addon SDK — stable API contract
   │       └── catppuccin-mocha.yaml   26 colors + 14 semantic roles
   └── Init.py / InitGui.py   Minimal log messages
 
-mods/ztools/                 [submodule] command provider (not a workbench)
-  ├── package.xml            Manifest (priority 50, depends on sdk)
-  ├── ztools/InitGui.py      Deferred command registration + _ZToolsManipulator
-  ├── ztools/ztools/
-  │   ├── commands/          Datum, pattern, pocket, assembly, spreadsheet
-  │   ├── datums/core.py     Datum creation via Part::AttachExtension
-  │   └── resources/         Icons (SDK theme tokens), theme utilities
-  └── CatppuccinMocha/       Theme preference pack (QSS)
+mods/gears/                  [submodule → gears.git] Gears workbench
+  ├── package.xml            Manifest (priority 40, depends on sdk)
+  └── ...                    Parametric gear generation
+
+mods/solver/                 [submodule → solver.git] Solver addon
+  └── ...                    Solver plugin support
 
 mods/silo/                   [submodule → silo-mod.git] FreeCAD workbench
   ├── freecad/package.xml    Manifest (priority 60, depends on sdk)