feat(compiler): list literals, typed compound assignment, file:line diagnostics

- `[a, b, c]` list literals (E_LIST → emit_list); static_type learns
  slice-element, `new T`, list, string and literal kinds
- `x op= y` lowers through the same path as `x = x op y` (emit_bin_vals):
  fixed `*=`/`/=` use the Q16.16 64-bit paths, string `+=` concatenates,
  int→long widens; unary `-` keeps a fixed operand's type (arith_ty)
- one `unescape()` table for "strings", 'chars' and `interpolation`;
  `'\''`, `'\\'`, `'\"'` no longer read as 0; unterminated char literals
  and unexpected characters are errors instead of silently skipped
- every diagnostic is `file:line: error: msg` (g_parse_file / g_err_file,
  Node.file + Node.line set by node()); tok_desc() in expectation errors;
  duplicate `function` names and unknown `phase` names are reported in
  source terms (phase_id used to default unknown phases to Overlay)
- interpolation holes skip braces inside string literals
- hand-IR preludes move from the user `@fn_` prefix to `@lp_` so a user
  `is_ws` / `str_eq` / `path_join` no longer collides at link time
- `@ClearColor(expr)` accepts any constant expression; `Os.pid()` added
  (docs page + inventory); `str_starts()` in support/str
- main.ludic: `else if` flag ladder, char literals, stale script comments
- examples/lang/operators.ludic covers all of the above; os.ludic covers
  Os.pid; docs pages for Os.pid and the Overlay phase; ten changesets
- reseeded: selfhost/ludicc.seed.ll is the new compiler's own fixpoint

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

selfhost/backend/stdlib/emit_hash.ludic

@@ -50,12 +50,12 @@ function emit_hash_ns(meth: pointer, e: Node) -> Val {
   if (meth == "of") or (meth == "fnv1a") {          # FNV-1a 32-bit over the bytes
     g_uses_hashrt = true
     let s = emit_expr(e.kids[0])
-    return val(emit_bind(`call i32 @fn_hash_fnv1a(ptr {s.code})`), "int")
+    return val(emit_bind(`call i32 @lp_hash_fnv1a(ptr {s.code})`), "int")
   }
   if (meth == "of64") or (meth == "fnv1a_64") {     # FNV-1a 64-bit -> a `long`
     g_uses_hashrt = true
     let s = emit_expr(e.kids[0])
-    return val(emit_bind(`call i64 @fn_hash_fnv1a_64(ptr {s.code})`), "long")
+    return val(emit_bind(`call i64 @lp_hash_fnv1a_64(ptr {s.code})`), "long")
   }
   if (meth == "mix64") {                            # fmix64 avalanche of one long
     let x = emit_expr(e.kids[0])
@@ -64,7 +64,7 @@ function emit_hash_ns(meth: pointer, e: Node) -> Val {
   if (meth == "crc32") {                            # CRC-32 (IEEE) checksum
     g_uses_hashrt = true
     let s = emit_expr(e.kids[0])
-    return val(emit_bind(`call i32 @fn_hash_crc32(ptr {s.code})`), "int")
+    return val(emit_bind(`call i32 @lp_hash_crc32(ptr {s.code})`), "int")
   }
   if (meth == "mix") {                              # fmix32 avalanche of one int
     let x = emit_expr(e.kids[0])
@@ -84,7 +84,7 @@ function emit_hash_ns(meth: pointer, e: Node) -> Val {
     let t1 = emit_bind(`add i32 {g}, {sl}`)
     let t2 = emit_bind(`add i32 {t1}, {sr}`)
     seed = emit_bind(`xor i32 {seed}, {t2}`)
-    i = i + 1
+    i += 1
   }
   return val(seed, "int")
 }
@@ -95,7 +95,7 @@ function emit_hash_ns(meth: pointer, e: Node) -> Val {
 # prime, and a bitwise CRC-32 with the reflected poly 0xEDB88320. No libc, no
 # allocation, bit-identical on every target.
 function emit_hash_prelude() -> void {
-  emith("define i32 @fn_hash_fnv1a(ptr %s) {\n")
+  emith("define i32 @lp_hash_fnv1a(ptr %s) {\n")
   emith("entry:\n")
   emith("  %hp = alloca i32\n")
   emith("  store i32 -2128831035, ptr %hp\n")       # 0x811c9dc5 offset basis
@@ -121,7 +121,7 @@ function emit_hash_prelude() -> void {
   emith("  %hr = load i32, ptr %hp\n")
   emith("  ret i32 %hr\n")
   emith("}\n")
-  emith("define i64 @fn_hash_fnv1a_64(ptr %s) {\n")  # 64-bit FNV-1a, same shape, i64
+  emith("define i64 @lp_hash_fnv1a_64(ptr %s) {\n")  # 64-bit FNV-1a, same shape, i64
   emith("entry:\n")
   emith("  %hp = alloca i64\n")
   emith("  store i64 -3750763034362895579, ptr %hp\n")   # 0xcbf29ce484222325 offset basis
@@ -147,7 +147,7 @@ function emit_hash_prelude() -> void {
   emith("  %hr = load i64, ptr %hp\n")
   emith("  ret i64 %hr\n")
   emith("}\n")
-  emith("define i32 @fn_hash_crc32(ptr %s) {\n")
+  emith("define i32 @lp_hash_crc32(ptr %s) {\n")
   emith("entry:\n")
   emith("  %cp = alloca i32\n")
   emith("  store i32 -1, ptr %cp\n")                # init 0xFFFFFFFF