Named targets feature

[create2000]

This is the first of two commits implementing named targets support, as discussed in #3309

Changes in this PR:

• Adds support for (targets (:name file) ...) syntax
• Defines Static.named type in Targets_spec
• Parses bindings without changing evaluation logic
• Verifies syntax with parse tests

Coming Next:
The second commit will implement the actual variable expansion and validation:

1. Target variable resolution (%{target:name})
2. Duplicate name prevention
3. Full integration with action expansion

Test Plan:

• Verify existing tests pass
• Added syntax parsing tests

[gridbugs]

Just clarifying that we won't be able to merge this PR until it contains both the parser for the new named targets syntax and the ability to resolve named targets. I like the idea of keeping these two stages separate for ease of implementation/review, so keeping them as separate commits in the same PR makes sense (I can review them commit-by-commit rather than reviewing the entire PR at once).