fix(lsp): identifier array dimension no longer panics the analyzer [0099]

`Analyzer.resolveTypeNode` read the array `.length` node's `.int_literal`
union field unconditionally. For a named-const dimension (`MAX :: 4;
[MAX]u8`) that node is an `identifier`, so the access tripped Zig's
checked-union panic and `sx lsp` aborted on didOpen. The main compiler
was unaffected (it folds the dim through the IR).

- New `arrayDimLength` helper switches on the dimension node tag:
  int_literal → value; identifier → a recorded module-const int value;
  anything else / out-of-u32-range → unknown. Never assumes a node shape.
- `Type.ArrayTypeInfo.length` is now `?u32`; null is an explicit "editor
  couldn't fold this dimension" marker (rendered `[_]T`), never a
  fabricated concrete length.
- New `const_int_values` registry records integer-literal consts at
  registration time for the identifier path.

Regression: first `src/lsp/*.test.zig` (the minimal LSP harness), wired
into the test graph via `src/root.zig`. Drives `analyzeDocument` over
`[MAX]u8` (folds to 4, no panic), `[64]u8` (happy-path guard), and
`[N]u8` (explicit unknown). Fail-before/pass-after verified.

Sibling audit of the resolveTypeNode/fieldType family: the array dim was
the only unchecked union-field access; all other arms recurse or
tag-check first. Noted a non-crashing display gap in server.zig hover
rendering for step B.

src/root.zig

@@ -22,6 +22,7 @@ pub const lsp = struct {
     pub const transport = @import("lsp/transport.zig");
     pub const types = @import("lsp/types.zig");
     pub const document = @import("lsp/document.zig");
+    pub const document_tests = @import("lsp/document.test.zig");
 };
 
 test {
@@ -35,6 +36,7 @@ test {
     // struct deeper, so reference them directly to pull in their tests.
     _ = lsp.server;
     _ = lsp.document;
+    _ = lsp.document_tests;
     _ = lsp.types;
     _ = lsp.transport;
 }