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>

changes/char-escapes.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+Character literals accept the same escapes as strings (`'\''`, `'\\'` and `'\"'` were silently read as 0); an unterminated character literal is now an error.

changes/clearcolor-expr.md

@@ -0,0 +1,3 @@
+bump: patch
+type: feat
+`@ClearColor(expr)` takes any constant expression, so a named palette colour (`@ClearColor(COLOR_FLOOR)`) works as well as a hex literal.

changes/compound-assign-types.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+`x += y` / `-=` / `*=` / `/=` now lower exactly like `x = x op y`: a Q16.16 `fixed` multiplies and divides through the 64-bit path, a string `+=` concatenates, and an `int` added to a `long` widens (they previously emitted raw integer arithmetic on the LLVM type).

changes/diagnostics-file-line.md

@@ -0,0 +1,3 @@
+bump: minor
+type: feat
+Every compiler diagnostic is reported as `file:line: error: message` — the file the line really lives in, even through imports — so editors can jump to it. Unexpected characters are errors (they used to be skipped silently), and defining one `function` twice is reported in source terms instead of failing in the IR assembler.

changes/formatter-brackets.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+`ludic-fmt` keeps `rows[i]`, `new []int`, `s[a..b]`, `emit(…)`, `~x` and list-literal braces tight, and recognises `<< >> & | ^ ~` as operators.

changes/interp-braces.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+A `{` or `}` inside a string literal within an interpolation hole (`` `{f("{")}` ``) is text, not structure; the hole scanner used to miscount it.

changes/list-literals.md

@@ -0,0 +1,3 @@
+bump: minor
+type: feat
+`[a, b, c]` list literals build a slice in place; the first element fixes the element type, later elements must match, and `[]` is an error (use `new []T`). Tables of records read as `[Row { … }, Row { … }]`.

changes/os-pid.md

@@ -0,0 +1,3 @@
+bump: minor
+type: feat
+`Os.pid()` returns the process id, for scratch files that concurrent runs of one tool must not share.

changes/prelude-symbol-prefix.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+Hand-written runtime preludes (string, Os.*, Fs.*, Crypto.*, …) now live under their own `@lp_` symbol prefix, so a user `function` named `is_ws`, `str_eq`, `path_join` and the like no longer collides with them at link time.

changes/unary-minus-fixed.md

@@ -0,0 +1,3 @@
+bump: patch
+type: fix
+Unary minus keeps its operand type: `-f` on a `fixed` is a `fixed` (it was typed `int`, which broke mixed arithmetic and comparisons).