[wasm] R2R OSR pinnedlocal hits fFrameWasUnwound and cycles while dumping frames

### Description

When the browser-wasm CoreCLR `JIT/opt/OSR/pinnedlocal` test is crossgened and run as ReadyToRun code, its out-of-process preflight asserts in `StackFrameIterator::Filter` at `stackwalk.cpp:1721` because `fFrameWasUnwound` is false. The subsequent diagnostic frame dump repeatedly reports the same `InlinedCallFrame` until the existing 300-second watchdog terminates the test.

This was observed while validating #133276 at commit `bec55a87be6f2f77518cc9316e57330454b98897`. It is being tracked separately because an exact R2R baseline control has not yet established whether that change introduced the failure. The interpreter control passes this test.

### Reproduction Steps

1. Check out dotnet/runtime with #133276 at `bec55a87be6f2f77518cc9316e57330454b98897`.
2. Build browser-wasm Checked CoreCLR and generate a crossgen2 layout:

```bash
export PATH="$PWD/artifacts/pyshim:$PWD/.dotnet:$PATH"
./build.sh clr -os browser -rc checked
./src/tests/build.sh generatelayoutonly crossgen2 checked \
-arch wasm -os browser -p:HostConfiguration=Release
```

3. Clear stale `JIT/opt` IL-CG2 images and run the generated `JIT.opt` wrapper with ReadyToRun enabled:

```bash
export CORE_ROOT="$PWD/artifacts/tests/coreclr/browser.wasm.Checked/Tests/Core_Root"
RunCrossGen2=1 bash JIT.opt.sh -coreroot="$CORE_ROOT"
```

The failure occurs during the out-of-process preflight for `JIT/opt/OSR/pinnedlocal`.

### Expected behavior

`JIT/opt/OSR/pinnedlocal` completes successfully under browser-wasm ReadyToRun, as it does with ReadyToRun disabled.

### Actual behavior

The test asserts at `src/coreclr/vm/stackwalk.cpp:1721`:

```text
fFrameWasUnwound
```

The diagnostic dump then repeatedly emits the same `InlinedCallFrame` and does not terminate normally. The existing 300-second watchdog eventually ends the test.

### Regression?

Unknown. The failure was observed on #133276, but no exact baseline R2R control has been run, so it should not be attributed to that PR. The interpreter control passes.

### Known Workarounds

Run the test with ReadyToRun disabled (`DOTNET_ReadyToRun=0`). The test passes in that configuration.

### Configuration

- CoreCLR browser-wasm
- Checked runtime
- ReadyToRun image generated with crossgen2
- macOS ARM64 build host
- Node.js 23.11.1
- Test sets `DOTNET_GCStress=3`

### Other information

This is distinct from:

- #133219 and the cooperative GC-mode assertion seen in other wasm R2R tests;
- #133264 / #133266, which address wasm virtual-IP classification during funclet stack walks.

The observed cyclic `InlinedCallFrame` dump suggests the frame chain or unwind state should be investigated at the first `fFrameWasUnwound` assertion rather than treating the watchdog termination as the root cause.

> [!NOTE]
> This issue was created with GitHub Copilot.

Start with src/coreclr/vm/stackwalk.cpp:1721 and reproduce JIT/opt/OSR/pinnedlocal using the browser-wasm ReadyToRun commands in the issue. Compare an exact R2R baseline with the #133276 build, then inspect the first fFrameWasUnwound assertion and repeated InlinedCallFrame dump. Done means the test completes successfully with ReadyToRun enabled and the frame dump no longer cycles.

Written by the indexing model from the issue text.