feat: add blu-site static site generator and fix language issues

Build a complete static site generator in Lux that faithfully clones
blu.cx (elmstatic). Generates 14 post pages, section indexes, tag pages,
and a home page with snippets grid from markdown content.

Language fixes discovered during development:
- Add \{ and \} escape sequences in string literals (lexer)
- Register String.indexOf and String.lastIndexOf in type checker
- Fix formatter to preserve brace escapes in string literals
- Improve LSP hover to show documentation for let bindings and functions

ISSUES.md documents 15 Lux language limitations found during the project.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

projects/blu-site/util.lux

@@ -0,0 +1,91 @@
+// Utility functions for the static site generator
+
+// Escape HTML special characters
+pub fn escapeHtml(s: String): String =
+    String.replace(String.replace(String.replace(s, "&", "&amp;"), "<", "&lt;"), ">", "&gt;")
+
+// Extract slug from a filename like "2025-01-29-blog-revamped.md"
+// Returns "2025-01-29-blog-revamped"
+pub fn slugFromFilename(filename: String): String = {
+    if String.endsWith(filename, ".md") then
+        String.substring(filename, 0, String.length(filename) - 3)
+    else
+        filename
+}
+
+// Format ISO date "2025-01-29" to "2025 Jan 29"
+pub fn formatDate(isoDate: String): String = {
+    if String.length(isoDate) < 10 then isoDate
+    else {
+        let year = String.substring(isoDate, 0, 4);
+        let month = String.substring(isoDate, 5, 7);
+        let day = String.substring(isoDate, 8, 10);
+        let monthName = if month == "01" then "Jan"
+            else if month == "02" then "Feb"
+            else if month == "03" then "Mar"
+            else if month == "04" then "Apr"
+            else if month == "05" then "May"
+            else if month == "06" then "Jun"
+            else if month == "07" then "Jul"
+            else if month == "08" then "Aug"
+            else if month == "09" then "Sep"
+            else if month == "10" then "Oct"
+            else if month == "11" then "Nov"
+            else "Dec";
+        year + " " + monthName + " " + day
+    }
+}
+
+// Recursively walk a directory, returning all file paths
+pub fn walkDir(path: String): List<String> with {File} = {
+    let entries = File.readDir(path);
+    List.fold(entries, [], fn(acc: List<String>, entry: String): List<String> => {
+        let fullPath = path + "/" + entry;
+        if File.isDir(fullPath) then
+            List.concat(acc, walkDir(fullPath))
+        else
+            List.concat(acc, [fullPath])
+    })
+}
+
+// Insertion sort by date string (descending — newest first)
+// Each item is (date, item) tuple
+pub fn sortByDateDesc(items: List<(String, String, String, String, String)>): List<(String, String, String, String, String)> = {
+    List.fold(items, [], fn(sorted: List<(String, String, String, String, String)>, item: (String, String, String, String, String)): List<(String, String, String, String, String)> =>
+        insertByDate(sorted, item)
+    )
+}
+
+fn insertByDate(sorted: List<(String, String, String, String, String)>, item: (String, String, String, String, String)): List<(String, String, String, String, String)> = {
+    let itemDate = item.0;
+    match List.head(sorted) {
+        None => [item],
+        Some(first) => {
+            let firstDate = first.0;
+            // Compare dates as strings — ISO format sorts lexicographically
+            if itemDate >= firstDate then
+                List.concat([item], sorted)
+            else
+                match List.tail(sorted) {
+                    Some(rest) => List.concat([first], insertByDate(rest, item)),
+                    None => [first, item]
+                }
+        }
+    }
+}
+
+// Get just the filename from a path
+pub fn basename(path: String): String = {
+    match String.lastIndexOf(path, "/") {
+        Some(idx) => String.substring(path, idx + 1, String.length(path)),
+        None => path
+    }
+}
+
+// Get the directory part of a path
+pub fn dirname(path: String): String = {
+    match String.lastIndexOf(path, "/") {
+        Some(idx) => String.substring(path, 0, idx),
+        None => "."
+    }
+}