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/game/emit_query.ludic

@@ -4,7 +4,7 @@
 
 function find_arch_id(name: pointer) -> int {
   var i = 0;  var n = 1
-  while i < len(prog) { if prog[i].kind == N_ARCH { if (prog[i].s == name) { return n };  n = n + 1 };  i = i + 1 }
+  while i < len(prog) { if prog[i].kind == N_ARCH { if (prog[i].s == name) { return n };  n += 1 };  i += 1 }
   return 0
 }
 
@@ -13,7 +13,7 @@ function emit_query(st: Node) -> void {
   let ip = emit_alloca("i32")
   store_at("i32", "0", ip)
   if nself < len(self_stk) { self_stk[nself] = ip } else { push(self_stk, ip) }
-  nself = nself + 1
+  nself += 1
 
   let cond = lbl("qcond");  let body = lbl("qbody");  let nxt = lbl("qnext");  let endl = lbl("qend")
   emit("  br label %");  emit(cond);  emit("\n")
@@ -54,7 +54,7 @@ function emit_query(st: Node) -> void {
     let keep = lbl("qt")
     emit("  br i1 ");  emit(ok);  emit(", label %");  emit(keep);  emit(", label %");  emit(nxt);  emit("\n")
     emit(keep);  emit(":\n")
-    t = t + 1
+    t += 1
   }
 
   # bind the requested components to the loop variables, in order
@@ -70,10 +70,10 @@ function emit_query(st: Node) -> void {
         let vslot = emit_alloca("ptr")
         emit("  store ptr ");  emit(slot);  emit(", ptr ");  emit(vslot);  emit("\n")
         loc_push(st.kids[vi].s, vslot, tm.s)
-        vi = vi + 1
+        vi += 1
       }
     }
-    t = t + 1
+    t += 1
   }
 
   # optional where-clause
@@ -97,5 +97,5 @@ function emit_query(st: Node) -> void {
   store_at("i32", i3, ip)
   emit("  br label %");  emit(cond);  emit("\n")
   emit(endl);  emit(":\n");  g_term = false
-  nself = nself - 1
+  nself -= 1
 }