chore: remove dead parse_comptime_decl method from parser (#28)

`parse_comptime_decl` was never called -- the `comptime` top-level
declaration is handled inline in `parse_top_level` (the `Some(TokenKind::Comptime)`
arm reads `comptime`, optionally branches to `parse_orchestrate_decl`,
and otherwise builds a `ComptimeDecl` directly from the block). The
separate helper was a leftover from an earlier factoring.

Identified during the #22 dead-code review (PR4 / #26) but deferred at
the time to avoid merge-conflict risk with the depth-guard PR #21 also
modifying parser.rs. With #21 merged this is a one-method delete.

Tests: `cargo test -p my-lang --lib parser::` -- 32/32 pass (same count
as before; the method had no associated tests).

Clippy: the lone `parse_comptime_decl is never used` warning at
parser.rs:825 is now gone.

Author: hyperpolymath

crates/my-lang/src/parser.rs

@@ -818,18 +818,6 @@ impl Parser {
         Ok(items)
     }
 
-    // ============================================
-    // Comptime Declaration
-    // ============================================
-
-    fn parse_comptime_decl(&mut self) -> ParseResult<ComptimeDecl> {
-        let start = self.current_span();
-        self.expect(TokenKind::Comptime)?;
-        let block = self.parse_block()?;
-        let span = self.span_from(start);
-        Ok(ComptimeDecl { block, span })
-    }
-
     // ============================================
     // Contract
     // ============================================