fix(rust): resolve self.field.method() on the field's declared type instead of a same-named method (#1585) (#1599)

Fixes #1585. **Stacked on #1596** (the base branch is `fix/1588-rust-impl-type-qualification`; this PR's own diff is the second commit). Merge #1596 first, then retarget/merge this one.

## What was wrong

```rust
impl Outer {
    pub fn run(&mut self) {
        self.inner.run();      // inner: Inner
    }
}
```

produced `Outer::run -> Outer::run` — recursion the source doesn't contain. The extractor collapsed every `self.<field>.<method>()` receiver to the bare method name (`run`), so the resolver only ever saw `run` and exact-matched the nearest same-named method — the calling method itself, or a method of an unrelated type. Nothing marked the edge as a guess, and no row stayed in `unresolved_refs`, so a consumer had no way to tell.

The same happened when the field's type isn't a project type at all (`its: std::vec::IntoIter<_>` → `self.its.next()`, `matcher: Regex` → `self.matcher.is_match()`): the bare `next` / `is_match` attached to whatever local method shared the name. ripgrep had 279 self-edges on `main`; the issue lists three sites, all of this shape.

(The issue's C++ control — "`Outer::run -> Inner::run` resolves correctly" — doesn't actually hold on `main`: `inner.h` is classified as C by the `.h` heuristic, so `Inner::run` never exists and the C++ repro self-edges too. That's #1592, fixed separately.)

## What this does

Rust struct fields are not graph nodes, so the field's type can only come from the struct's declaration text. This follows the Go 2-hop precedent exactly (`matchGoFieldChainCall`, #1276), including its exclusivity rule:

1. **Extraction (TS walker + native kernel, identical, parity-tested):** a call whose receiver is `self.<field>` keeps the owner-field shape — `self.inner.run()` is emitted as `self.inner.run`. Deeper chains (`self.a.b.m()`), call receivers (`self.f().m()`), parenthesized receivers and bare `self` keep the bare name, exactly as before.
2. **Resolution (`matchRustSelfFieldCall`):** owner type = the calling method's qualified-name prefix (`Outer::run` → `Outer`); the field's declared type is read from the owner struct's **own declaration lines** (comment-stripped, line by line — same discipline as the Go helper); the method is resolved **and validated** on that type by `resolveMethodOnType` (confidence 0.85, `instance-method`).
3. **Exclusive:** when the field is declared with an external type, a generic parameter (`T`), a container that doesn't auto-deref (`Option`/`Vec`/`Mutex`/…), or can't be found, the ref **stays unresolved** — it never falls through to the bare-name strategies. That is the safe behaviour the issue asks for, and it is what #1276 already chose for Go.

`rustFieldTypeName` looks through exactly the layers Rust's method-call auto-deref looks through: references (`&`, `&'a mut`) and the owning smart pointers `Box`/`Rc`/`Arc`. `Box<dyn Source>` yields the trait, whose method node the interface-impl synthesizer then fans out to every implementation. `Option<Inner>` is left alone — `self.inner.take()` is Option's method and must not become `Inner::take`.

Why it stacks on #1596: the owner is taken from the method's qualified name, which for a generic/lifetime impl was the trait's name before that fix.

## Measured on ripgrep (110 `.rs` files, #1596 build vs this branch)

| | #1596 | this PR |
|---|---|---|
| nodes | 4029 | 4029 |
| `calls` self-edges | 279 | **146** (none of the `self.<field>` shape remain — 116 bare-receiver, 30 other dotted) |
| `self.<field>.m()` calls resolved through a validated field type | — | **292** (`DecompressionMatcher::command -> GlobSet::matches`, `Parser::find_long -> FlagMap::find`, `Haystack::path -> DirEntry::path`, …) |
| `self.<field>.m()` calls left unresolved | — | **417** — every sampled one is a std/container method: `self.commands.push`, `self.child.wait`, `self.pre.is_some`, `self.colors.clone`, `self.path_terminator.unwrap_or` |
| `calls` edges total | 9150 | 8878 (the 272 removed are the former bare-name guesses for those 417) |

The issue's three sites: `walk.rs:824` now resolves to `IgnoreBuilder::add_custom_ignore_filename` (was a self-edge); `walk.rs:1195` (`self.its.next`, `IntoIter`) and `globset/lib.rs:983` (`self.matcher.is_match`, `Regex`) are parked as unresolved instead of guessed.

The issue's repro gives `Outer::run -> Inner::run` (`instance-method`, confidence 0.85) on both the kernel path and `CODEGRAPH_KERNEL=0`.

## Tests

- `__tests__/extraction.test.ts`: only the single-hop `self.<field>.<method>()` call keeps the prefix; deeper / call / parenthesized / bare-`self` receivers and a local receiver are unchanged.
- `__tests__/resolution.test.ts` (end-to-end, Cargo layout): the issue's repro → `Outer::run -> Inner::run`, no self-edge; an external field type (`std::vec::IntoIter`) with a local `next` decoy → no edge at all; `Box<Inner>` and `&'a mut Inner` resolve, `Option<Inner>` does not (even though `Inner` declares the method); a generic `T` field → no edge; genuine `self.run()` recursion keeps its self-edge; the #1588 repro's `UsesFile::go` / `UsesBuf::go` resolve to `FileSource::read` / `BufSource::read`, and a `Box<dyn Source>` field lands on `Source::read` with the synthesizer fanning out to both impls.
- `__tests__/fixtures/kernel-parity/torture.rs` grows the receiver shapes; all 15 kernel parity suites pass against the rebuilt kernel (147 tests).
- Full `npm test` on this branch: 189 files, 3187 passed, 9 skipped, 0 failed.

Re-index after upgrading.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_01LxZj6W6Y1SHXwvpT3uwJpK

__tests__/fixtures/kernel-parity/torture.rs

@@ -72,6 +72,16 @@ impl Widget {
         self.n * mul()
     }
 
+    /// Receiver shapes (#1585): only `self.<field>.<method>()` keeps the
+    /// owner-field prefix; deeper / parenthesized / call / bare-self collapse.
+    fn via_field(&self) -> u32 {
+        self.field.deep_call();
+        self.field.z.clone();
+        self.method_a().chain_b();
+        (self.field).deep_call();
+        self.area()
+    }
+
     fn clone_self(&self) -> Self {
         Self::assoc();
         Widget {