☂️ hrw4u: split visitor.py into three passes (AST → sema → emitter)

[masaori335]

tools/hrw4u/src/visitor.py — 1,208 LoC, 20 visit* methods — does all of this in one pass:

• resolves symbols
• checks hook validity and arguments
• applies sandbox policy
• allocates variable slots
• expands procedures by splicing source text
• and renders .conf

I'd break it into three: an AST, a semantic-analysis pass (sema), and a .conf emitter. It is a refactor — no C++ changes, no grammar changes, no .conf output changes.

What the split buys

	Today	After
Where a new check lives	a visit* method inside a 1,208-line file whose other job is text rendering	a function over the resolved tree
When a check can run	only while .conf is being produced	whenever the tree exists
What the language server runs	the whole compiler, .conf emission included, on every keystroke — and reads visitor._proc_registry, a private field	sema, and stops there
Diagnostics	built from CST contexts inside the emitter	built from AST spans in sema — one wording for CLI and editor
The typed AST from #13126	test-only and lossy; nothing consumes it	the production tree
.conf emission	the tail of the compiler	one consumer of the tree

What it makes possible later

Because .conf emission becomes a consumer of the resolved tree rather than the compiler's tail,
another consumer can attach at the same point without touching the first — and any check added to
sema lands for both. That is the reason no .conf text appears in any sema_nodes node: the fork
point has to be format-neutral or it is not a fork point.

Tracking

• hrw4u: Add AST for static analysis and codegen #13126
• hrw4u: record spans, comments and operand forms in the AST #13665
• semantic-analysis
• hrw (.conf) emitter

Related but independent

• hrw4u: exit non-zero on compile errors #13656