Fix/clipboard layout type detection 2

.cursor/skills/custom-function-build/SKILL.md

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+---
+name: custom-function-build
+description: Create a new FileMaker custom function and deploy it to the clipboard for pasting into Manage Custom Functions. Use when the developer asks to create, add, or write a custom function. Produces fmxmlsnippet XML with the XMFN clipboard class.
+---
+
+# Custom Function Build
+
+Generate a FileMaker custom function as `fmxmlsnippet type="FMObjectList"` with `<CustomFunction>` as the root element. Deploy via `clipboard.py` (auto-detects `XMFN`).
+
+---
+
+## Step 1: Gather context
+
+Before writing, check whether the function already exists:
+
+```bash
+grep -r "name=\"FunctionName\"" agent/xml_parsed/custom_function_calcs/*/
+```
+
+Also check `agent/CONTEXT.json` → `custom_functions` section if present. If the function exists, read it and modify rather than creating from scratch.
+
+---
+
+## Step 2: Write the XML
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<fmxmlsnippet type="FMObjectList">
+  <CustomFunction id="0" functionArity="N" visible="True" parameters="param1 ; param2" name="FunctionName">
+    <Calculation><![CDATA[
+...calculation body...
+    ]]></Calculation>
+  </CustomFunction>
+</fmxmlsnippet>
+```
+
+### Attribute rules
+
+| Attribute       | Value                                                                                 |
+|-----------------|---------------------------------------------------------------------------------------|
+| `id`            | Use `0` — FileMaker auto-assigns on paste                                             |
+| `functionArity` | Number of parameters (0 for no params)                                                |
+| `visible`       | `"True"` = public (callable from any calculation); `"False"` = private               |
+| `parameters`    | Parameter names separated by ` ; ` (space-semicolon-space). Empty string if no params |
+| `name`          | The function name exactly as it will appear in FileMaker                              |
+
+### Calculation body rules
+
+- Wrap in `<![CDATA[...]]>` — no XML escaping needed inside
+- Use FileMaker native functions and operators
+- Parameter names in the body must match the `parameters` attribute exactly
+- Recursive functions reference themselves by name — FileMaker supports recursion natively
+- Follow `agent/docs/CODING_CONVENTIONS.md` — Let() formatting, operator spacing, etc.
+- Never invent function names — validate against `agent/docs/filemaker/functions/` if available
+
+### Common patterns
+
+**No parameters (constant):**
+```xml
+<CustomFunction id="0" functionArity="0" visible="True" parameters="" name="AppVersion">
+  <Calculation><![CDATA["2.1.0"]]></Calculation>
+</CustomFunction>
+```
+
+**Single parameter:**
+```xml
+<CustomFunction id="0" functionArity="1" visible="True" parameters="n" name="NumToLetter">
+  <Calculation><![CDATA[Char ( 64 + n )]]></Calculation>
+</CustomFunction>
+```
+
+**Multiple parameters:**
+```xml
+<CustomFunction id="0" functionArity="2" visible="True" parameters="value ; decimals" name="RoundTo">
+  <Calculation><![CDATA[Round ( value ; decimals )]]></Calculation>
+</CustomFunction>
+```
+
+**Recursive (e.g. extended alpha — 27→AA, 28→AB…):**
+```xml
+<CustomFunction id="0" functionArity="1" visible="True" parameters="n" name="NumToLetterExt">
+  <Calculation><![CDATA[
+If ( n <= 26 ;
+	Char ( 64 + n ) ;
+	NumToLetterExt ( Ceiling ( n / 26 ) - 1 ) & Char ( 64 + Mod ( n - 1 ; 26 ) + 1 )
+)
+  ]]></Calculation>
+</CustomFunction>
+```
+
+---
+
+## Step 3: Deploy
+
+Write the XML to `agent/sandbox/{FunctionName}.xml`, then copy to clipboard:
+
+```bash
+python3 agent/scripts/clipboard.py write agent/sandbox/FunctionName.xml
+```
+
+`clipboard.py` auto-detects `XMFN` from the `<CustomFunction>` element — no `--class` flag needed.
+
+### Paste instructions
+
+> The custom function is on your clipboard.
+>
+> 1. Open **File > Manage > Custom Functions**
+> 2. Click **Import** (or **⌘V** if FM supports direct paste — varies by version)
+> 3. If paste doesn't work, click **New**, name it **{FunctionName}**, paste the calculation body manually
+
+> **Note:** FileMaker 19+ supports pasting `<CustomFunction>` snippets directly into the Manage Custom Functions dialog via ⌘V. Earlier versions require manual entry.
+
+---
+
+## Constraints
+
+- One `<CustomFunction>` element per snippet — FM only pastes the first if multiple are present
+- `functionArity` must exactly match the number of parameters in the `parameters` attribute
+- Private functions (`visible="False"`) are not callable from layout calculations or scripts — only from other custom functions
+- Custom function names are global across the file — check for conflicts before creating
+- Never modify files in `agent/xml_parsed/` — copy to `agent/sandbox/` first