M2: MSVC C++ demangler + demangled_names DB table

Adds an MSVC name-demangling layer in front of M3's vtable / RTTI work:
- New `xenia_analysis::demangle` wraps the `msvc-demangler` crate (a Rust
  port of LLVM's `MicrosoftDemangle.cpp`). `demangle()` short-circuits on
  non-mangled inputs (`?` prefix check); `demangle_or_raw()` always returns
  a record (raw passthrough on parse failure).
- Heuristic split of the formatted demangled string into structured fields
  `(namespace_path, class_name, method_name, params_signature)`. Top-level
  paren / template-bracket aware, so `a::b<c::d>::e` and signatures with
  templated arg types parse correctly.
- DB: new `demangled_names(address, mangled, raw_demangled, namespace_path,
  class_name, method_name, params_signature)` with indices on address /
  class_name / method_name. Populated from any label whose name starts with
  `?` plus any import name that happens to be mangled.

For Sylpheed (a fully stripped binary) this table is empty out-of-the-box;
the layer's value lands in M3, which will append rows for every RTTI
TypeDescriptor name found in `.rdata`.

Tests 610→617 (+7 demangler unit tests covering early-out, raw fallback,
member function form, RTTI form, qname split, paren-template safety, and
top-level `::` splitting).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/xenia-analysis/Cargo.toml

@@ -14,3 +14,4 @@ anyhow = { workspace = true }
 tracing = { workspace = true }
 metrics = { workspace = true }
 duckdb = { workspace = true }
+msvc-demangler = "0.11"