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/frontmatter.lux

@@ -0,0 +1,79 @@
+// YAML-like frontmatter parser
+// Parses the --- delimited frontmatter block from markdown files
+
+pub type Frontmatter =
+    | Frontmatter(String, String, String, String)
+    //             title   date    desc    tagsRaw
+
+pub type ParseResult =
+    | ParseResult(Frontmatter, String)
+    //             front       body
+
+pub fn parse(content: String): ParseResult = {
+    let lines = String.lines(content);
+    // Skip first --- line, collect key: value pairs until next ---
+    let result = List.fold(lines, (false, false, "", "", "", "", ""), fn(acc: (Bool, Bool, String, String, String, String, String), line: String): (Bool, Bool, String, String, String, String, String) => {
+        let inFront = acc.0;
+        let pastFront = acc.1;
+        let title = acc.2;
+        let date = acc.3;
+        let desc = acc.4;
+        let tags = acc.5;
+        let body = acc.6;
+        if pastFront then
+            (inFront, pastFront, title, date, desc, tags, body + line + "\n")
+        else if String.trim(line) == "---" then
+            if inFront then
+                // End of frontmatter
+                (false, true, title, date, desc, tags, body)
+            else
+                // Start of frontmatter
+                (true, false, title, date, desc, tags, body)
+        else if inFront then {
+            // Parse key: value
+            match String.indexOf(line, ": ") {
+                Some(idx) => {
+                    let key = String.trim(String.substring(line, 0, idx));
+                    let rawVal = String.trim(String.substring(line, idx + 2, String.length(line)));
+                    // Strip surrounding quotes if present
+                    let val = if String.startsWith(rawVal, "\"") then
+                        String.substring(rawVal, 1, String.length(rawVal) - 1)
+                    else
+                        rawVal;
+                    if key == "title" then
+                        (inFront, pastFront, val, date, desc, tags, body)
+                    else if key == "date" then
+                        (inFront, pastFront, title, val, desc, tags, body)
+                    else if key == "description" then
+                        (inFront, pastFront, title, date, val, tags, body)
+                    else if key == "tags" then
+                        (inFront, pastFront, title, date, desc, val, body)
+                    else
+                        (inFront, pastFront, title, date, desc, tags, body)
+                },
+                None => (inFront, pastFront, title, date, desc, tags, body)
+            }
+        } else
+            (inFront, pastFront, title, date, desc, tags, body)
+    });
+    let front = Frontmatter(result.2, result.3, result.4, result.5);
+    ParseResult(front, result.6)
+}
+
+pub fn getTitle(f: Frontmatter): String =
+    match f { Frontmatter(t, _, _, _) => t }
+
+pub fn getDate(f: Frontmatter): String =
+    match f { Frontmatter(_, d, _, _) => d }
+
+pub fn getDesc(f: Frontmatter): String =
+    match f { Frontmatter(_, _, d, _) => d }
+
+pub fn getTagsRaw(f: Frontmatter): String =
+    match f { Frontmatter(_, _, _, t) => t }
+
+pub fn getTags(f: Frontmatter): List<String> =
+    match f { Frontmatter(_, _, _, t) =>
+        if t == "" then []
+        else String.split(t, " ")
+    }