feat(templates): document templating system for .kc files

Add a template system integrated with Silo new-item creation that lets
users create parts from pre-configured .kc templates and save existing
documents as reusable templates.

Changes:
- mods/silo: template discovery, picker UI, Save as Template command,
  3-tier search paths (system, personal, org-shared)
- docs: template guide, SUMMARY.md entry, silo.md command reference

docs/src/SUMMARY.md

@@ -12,6 +12,7 @@
 - [Workbenches](./guide/workbenches.md)
   - [ztools](./guide/ztools.md)
   - [Silo](./guide/silo.md)
+  - [Document Templates](./guide/templates.md)
 
 # Architecture
 
@@ -49,6 +50,16 @@
 - [Solver Service](./silo-server/SOLVER.md)
 - [Roadmap](./silo-server/ROADMAP.md)
 
+# Kindred Solver
+
+- [Overview](./solver/overview.md)
+- [Expression DAG](./solver/expression-dag.md)
+- [Constraints](./solver/constraints.md)
+- [Solving Algorithms](./solver/solving.md)
+- [Diagnostics](./solver/diagnostics.md)
+- [Assembly Integration](./solver/assembly-integration.md)
+- [Writing a Custom Solver](./solver/writing-a-solver.md)
+
 # Reference
 
 - [Configuration](./reference/configuration.md)

docs/src/guide/silo.md

@@ -53,6 +53,7 @@ The silo-mod repository was split from a monorepo into three repos: `silo-client
 | `Silo_TagProjects` | Multi-select dialog for assigning project tags to items |
 | `Silo_Rollback` | Select a previous revision and create a new revision from that point with optional comment |
 | `Silo_SetStatus` | Change revision lifecycle status: draft → review → released → obsolete |
+| `Silo_SaveAsTemplate` | Save a copy of the current document as a reusable [template](./templates.md) with metadata |
 
 ### Administration
 
@@ -129,9 +130,11 @@ mods/silo/
 ├── freecad/
 │   ├── InitGui.py             # SiloWorkbench registration
 │   ├── schema_form.py         # Schema-driven item creation dialog (SchemaFormDialog)
-│   ├── silo_commands.py       # 14 commands + dock widgets
+│   ├── silo_commands.py       # 15 commands + dock widgets
 │   ├── silo_origin.py         # FileOrigin backend
 │   ├── silo_start.py          # Native start panel (database items, activity feed)
+│   ├── templates.py           # Template discovery, filtering, injection
+│   ├── templates/             # System template .kc files + CLI injection tool
 │   └── resources/icons/       # 10 silo-*.svg icons
 ├── silo-client/               # Shared Python API client (nested submodule)
 │   └── silo_client/

docs/src/guide/templates.md

@@ -0,0 +1,140 @@
+# Document Templates
+
+Templates let you create new parts and assemblies from pre-configured `.kc` files. Instead of starting from a bare `App::Part` or `Assembly::AssemblyObject`, a template can include predefined tree structures, jobs, metadata, and workbench-specific features.
+
+## How templates work
+
+A template is a normal `.kc` file with an extra `silo/template.json` descriptor inside the ZIP archive. When you select a template during **Silo > New**:
+
+1. The template `.kc` is **copied** to the canonical file path
+2. `silo/template.json` and `silo/manifest.json` are **stripped** from the copy
+3. The document is **opened** in FreeCAD
+4. Silo properties (part number, item ID, revision, type) are **stamped** onto the root object
+5. On **save**, `kc_format.py` auto-creates a fresh manifest
+
+The original template file is never modified.
+
+## Using templates
+
+### Creating a new item from a template
+
+1. **Silo > New** (Ctrl+N)
+2. Select an **Item Type** (Part, Assembly, etc.)
+3. The **Template** dropdown shows templates matching the selected type and category
+4. Select a template (or leave as "No template" for a blank document)
+5. Fill in the remaining fields and click **Create**
+
+The template combo updates automatically when you change the item type or category.
+
+### Saving a document as a template
+
+1. Open the document you want to use as a template
+2. **Silo > Save as Template**
+3. Fill in the template metadata:
+   - **Name** — display name shown in the template picker (pre-filled from document label)
+   - **Description** — what the template is for
+   - **Item Types** — which types this template applies to (part, assembly, etc.)
+   - **Categories** — category prefix filter (e.g. `F`, `M01`); leave empty for all categories
+   - **Author** — pre-filled from your Silo login
+   - **Tags** — comma-separated search tags
+4. Click **Save Template**
+5. Optionally upload to Silo for team sharing
+
+The template is saved as a copy to your personal templates directory. The original document is unchanged.
+
+## Template search paths
+
+Templates are discovered from three locations, checked in order. Later paths shadow earlier ones by name (so you can override a system template with a personal one).
+
+| Priority | Path | Purpose |
+|----------|------|---------|
+| 1 (lowest) | `mods/silo/freecad/templates/` | System templates shipped with the addon |
+| 2 | `~/.local/share/FreeCAD/Templates/` | Personal templates (sister to `Macro/`) |
+| 3 (highest) | `~/projects/templates/` | Org-shared project templates |
+
+The personal templates directory (`Templates/`) is created automatically when you first save a template. It lives alongside the `Macro/` directory in your FreeCAD user data.
+
+## Template descriptor schema
+
+The `silo/template.json` file inside the `.kc` ZIP has the following structure:
+
+```json
+{
+  "template_version": "1.0",
+  "name": "Sheet Metal Part",
+  "description": "Body with SheetMetal base feature and laser-cut job",
+  "item_types": ["part"],
+  "categories": [],
+  "icon": "sheet-metal",
+  "author": "Kindred Systems",
+  "tags": ["sheet metal", "fabrication"]
+}
+```
+
+| Field | Type | Required | Description |
+|-------|------|----------|-------------|
+| `template_version` | string | yes | Schema version, currently `"1.0"` |
+| `name` | string | yes | Display name in the template picker |
+| `description` | string | no | Human-readable purpose |
+| `item_types` | string[] | yes | Controls visibility — `["part"]`, `["assembly"]`, or both |
+| `categories` | string[] | no | Category prefix filter. Empty array means all categories |
+| `icon` | string | no | Icon identifier (reserved for future use) |
+| `author` | string | no | Template author |
+| `tags` | string[] | no | Searchable metadata tags |
+
+### Filtering rules
+
+- **item_types**: The template only appears when the selected item type is in this list
+- **categories**: If non-empty, the template only appears when the selected category starts with one of the listed prefixes. An empty list means the template is available for all categories
+
+## Creating templates from the command line
+
+The `inject_template.py` CLI tool can inject `silo/template.json` into any `.kc` file:
+
+```bash
+cd mods/silo/freecad/templates/
+
+# Create a template from an existing .kc file
+python inject_template.py my-part.kc "My Custom Part" \
+    --type part \
+    --description "Part with custom features" \
+    --author "Your Name" \
+    --tag "custom"
+
+# Assembly template
+python inject_template.py my-assembly.kc "My Assembly" \
+    --type assembly \
+    --description "Assembly with predefined joint groups"
+
+# Template with category filtering
+python inject_template.py sheet-metal.kc "Sheet Metal Part" \
+    --type part \
+    --category S \
+    --category X \
+    --tag "sheet metal" \
+    --tag "fabrication"
+```
+
+## Module structure
+
+```
+mods/silo/freecad/
+├── templates.py               # Discovery, filtering, injection helpers
+├── templates/
+│   └── inject_template.py     # CLI tool for injecting template.json
+├── schema_form.py             # Template combo in New Item form
+└── silo_commands.py           # SaveAsTemplateDialog, Silo_SaveAsTemplate,
+                               # SiloSync.create_document_from_template()
+```
+
+### Key functions
+
+| Function | File | Purpose |
+|----------|------|---------|
+| `discover_templates()` | `templates.py` | Scan search paths for `.kc` files with `silo/template.json` |
+| `filter_templates()` | `templates.py` | Filter by item type and category prefix |
+| `inject_template_json()` | `templates.py` | Inject/replace `silo/template.json` in a `.kc` ZIP |
+| `get_default_template_dir()` | `templates.py` | Returns `{userAppData}/Templates/`, creating if needed |
+| `get_search_paths()` | `templates.py` | Returns the 3-tier search path list |
+| `create_document_from_template()` | `silo_commands.py` | Copy template, strip identity, stamp Silo properties |
+| `_clean_template_zip()` | `silo_commands.py` | Strip `silo/template.json` and `silo/manifest.json` from a copy |