Add grapho CLI with improved UX

New CLI features:
- One-liner health check as default (grapho)
- Component status dashboard (grapho status)
- Verbose mode with details (grapho status -v)
- System diagnostics with fix commands (grapho doctor)
- Machine-readable output (grapho --json)
- Actionable fix suggestions for all warnings/errors

Also adds documentation:
- docs/MARKDOWN-EDITORS.md - Editor recommendations for mobile/desktop
- docs/LUX-LIMITATIONS.md - Tracking Lux language issues

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/LUX-LIMITATIONS.md

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+# Lux Language Limitations (grapho CLI)
+
+This document tracks limitations encountered while developing the grapho CLI in Lux, to help improve the language.
+
+## Fixed Issues
+
+### 1. Double Execution Bug (FIXED)
+**Severity:** Critical
+**Status:** Fixed in Lux c_backend.rs
+
+When using `let result = run main() with {}` to invoke the main function, the entire program was executing twice.
+
+**Root Cause:** In `c_backend.rs:3878-3907`, the generated C code was:
+1. Executing all `run` expressions (including `run main() with {}`)
+2. Then ALSO calling `main_lux()` separately because `has_main` was true
+
+**Fix:** Added tracking of whether main was already called via a `run` expression, and skip the separate `main_lux()` call if so.
+
+---
+
+## String Handling Issues
+
+### 2. No Escape Sequences in String Literals
+**Severity:** High
+**Status:** Confirmed
+
+Lux does not support backslash escape sequences like `\"`, `\n`, `\t` in string literals.
+
+```lux
+// This FAILS - backslash causes parse error
+Console.print("Hello \"World\"")  // ERROR: Unexpected character: '\'
+
+// This FAILS
+Console.print("Line1\nLine2")  // ERROR: Unexpected character: '\'
+```
+
+**Impact:** Cannot include quotes in strings, cannot create multi-line strings, cannot output JSON with proper formatting.
+
+**Workaround:**
+- Use shell commands via `Process.exec` to generate quoted output
+- Use `String.fromChar('"')` for quotes (but this had issues too)
+- For JSON output, use key=value format instead
+
+### 3. Dollar Sign in Strings Causes Parse Error
+**Severity:** Medium
+**Status:** Confirmed
+
+The `$` character in strings triggers the string interpolation lexer, even inside shell command strings.
+
+```lux
+// This FAILS
+execQuiet("jq -n --arg x '$foo' ...")  // ERROR: Unexpected character: '$'
+```
+
+**Impact:** Cannot use shell variable syntax or jq arguments in command strings.
+
+**Workaround:** Avoid `$` in strings, or construct commands differently.
+
+### 4. String.fromChar Returns Int, Not String
+**Severity:** Medium
+**Status:** Bug
+
+`String.fromChar('"')` appears to return an Int instead of a String, causing C compilation errors.
+
+```lux
+let q = String.fromChar('"')  // Compiles but C code is wrong
+Console.print(q + "hello")    // C error: int + string
+```
+
+**Impact:** Cannot use character literals to build strings.
+
+**Workaround:** Use `execQuiet("printf '%s' '\"'")` to get a quote character.
+
+---
+
+## Type System Issues
+
+### 5. Record Type Definitions Don't Work as Expected
+**Severity:** Medium
+**Status:** Needs Investigation
+
+Defining a record type and then creating values of that type doesn't work:
+
+```lux
+type ComponentStatus = {
+    name: String,
+    status: HealthStatus,
+    message: String,
+    fix: String
+}
+
+fn checkNb(): ComponentStatus with {Process} = {
+    // ...
+    { name: "nb", status: Healthy, message: "ok", fix: "" }
+    // ERROR: Cannot unify { name: String, ... } with ComponentStatus
+}
+```
+
+**Impact:** Cannot use structured types for cleaner code organization.
+
+**Workaround:** Avoid record types, use multiple return values via tuples or restructure code.
+
+### 6. Int.parse Doesn't Exist or Has Wrong Signature
+**Severity:** Low
+**Status:** Confirmed
+
+There's no obvious way to parse a string to an integer.
+
+```lux
+let count = Int.parse(someString)  // ERROR: Unknown effect operation
+```
+
+**Impact:** Cannot convert string output from shell commands to numbers.
+
+**Workaround:** Keep numbers as strings, use shell for numeric comparisons.
+
+---
+
+## Suggestions for Lux
+
+1. **Add escape sequence support** - At minimum `\"`, `\\`, `\n`, `\t`
+2. **Fix String.fromChar** to return String, not Int
+3. **Add raw string literals** - Something like `r"..."` or `'''...'''` for shell commands
+4. **Fix the double execution bug** in the runtime
+5. **Support record type literals** matching their declared type
+6. **Add Int.parse and Float.parse** for string-to-number conversion
+7. **Consider a heredoc syntax** for multi-line strings with special characters
+
+---
+
+## Current Workarounds in grapho CLI
+
+1. **Double output:** FIXED in Lux c_backend.rs
+2. **JSON output:** Using key=value format instead of proper JSON
+3. **Quotes in output:** Avoided entirely or generated via shell
+4. **Structured types:** Using individual variables instead of records
+5. **Numeric parsing:** Keeping counts as strings throughout