feat: restore sentinel-slice file path interfaces

README.md

@@ -29,7 +29,7 @@ main proc() int {
 
 this prints `42`. `main` must be a top-level function with no parameters; nonvoid results are printed, not used as process exit statuses. the current macOS bootstrap obtains arguments from the native startup environment.
 
-source loading uses the supplied `io.Io` for opening, reading, and closing files. `io.open` accepts a borrowed zero-terminated pointer, including paths returned by `process.argument`. `io.read_all(allocator, reader, maximum)` reads to EOF into a caller-owned `ArrayList(u8)`; release it with `arraylist.deinit`. it frees partial storage on error and consumes one extra byte to distinguish an exact-size input from a limit violation. the driver maps `limit_exceeded` to `source_too_large` at its `u32` source-size limit.
+source loading uses the supplied `io.Io` for opening, reading, and closing files. `io.open` accepts a borrowed zero-terminated slice (`[;0]u8`), including arguments returned by `process.argument` without copying their storage. the bootstrap supports checked sentinel-slice construction with `pointer[..length;0]`. `io.read_all(allocator, reader, maximum)` reads to EOF into a caller-owned `ArrayList(u8)`; release it with `arraylist.deinit`. it frees partial storage on error and consumes one extra byte to distinguish an exact-size input from a limit violation. the driver maps `limit_exceeded` to `source_too_large` at its `u32` source-size limit.
 
 the parser supports arithmetic expressions with nested parenthesized groups, such as `a + (b - c) * 2 / 3`. groups control precedence without adding AST nodes; inner expression spans exclude the grouping parentheses. parsing accepts integer division syntax, but type checking requires float operands for `/`.