fix(cpp): compose namespace prefix into out-of-line method qualified names (#1310)

An out-of-line member definition inside a namespace block takes its
qualifiedName from the declarator's receiver, which is spelled RELATIVE
to the enclosing namespace — so `namespace simulator {
ManifestStartup::Output ManifestStartup::Apply(...) {} }` indexed as
ManifestStartup::Apply while the class node carried
simulator::ManifestStartup. Fully-qualified call sites
(simulator::ManifestStartup::Apply(...)) never resolved; callers and
file impact came up empty (#1291).

The receiver-based qualifiedName now composes the active namespace
prefix, anchored at the first prefix segment the receiver re-spells
(so `namespace sim { void sim::M::f() {} }` doesn't double-prefix).
namespacePrefix is only ever non-empty for C++ — Go/Rust/Kotlin/Lua
receivers pass through unchanged.

leveldb re-index: node count byte-stable (3,044), calls edges +6,
namespace-qualified method names 947 -> 1,252.

Fixes #1291

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Fixes
 
+- C++ methods defined out-of-line inside a namespace (`namespace sim { Output MyClass::Apply(...) { ... } }`) now carry the namespace in their qualified name, matching their class. Fully-qualified call sites from other files (`sim::MyClass::Apply(...)`) resolve to the definition again, so `codegraph callers` and file impact no longer come up empty for this pattern. (#1291)
 - C++ methods defined out-of-line on a template class (`template <typename T> T Box<T>::get() { ... }`) no longer keep the template parameter list in their qualified name. They now index as `Box::get` — identical to an inline definition of the same method — so they link to their class and resolve from call sites again, and pathological multi-line template parameter lists can no longer blow the qualified name past filesystem name limits. (#1286)
 - Go route detection no longer misidentifies ordinary method calls that share HTTP verb names — `cache.Put("key", value)`, `store.Get("config", out)`, `bus.Handle("user.created", handler)` and the like were being indexed as HTTP routes, polluting route listings in cache-heavy codebases. A registration now has to look like one: its first argument must be a `/`-prefixed path (all routers) or a Go 1.22 `"METHOD /path"` pattern on `Handle`/`HandleFunc`, which now also extracts the method instead of listing the route as `ANY`. (#1259)
 - Progress output on Windows no longer mixes ASCII `|` rails with the Unicode `│ ◆ ●` frame around them. In terminals that render Unicode (Windows Terminal, VS Code, ConEmu/Cmder, JetBrains, Alacritty), the whole `codegraph init` / `index` / `sync` block now draws with matching box-drawing characters; unrecognized legacy consoles keep the safe all-ASCII output that avoids garbled characters. `CODEGRAPH_ASCII=1` / `CODEGRAPH_UNICODE=1` still override in either direction. (#398)