Reference counts cannot remove unreachable recursive functions because their self- and mutual references keep the counts nonzero even when no executable code can reach them.

This change computes function reachability after scoping is flushed. Normalize registers function declarations and bindings with implicit runtime observers. References outside registered functions make their targets live; references owned by a live registered function propagate liveness to their targets.

Graph deadness is used only to remove function declarations. Other transformations continue to use ordinary reference counts together with implicit-observability checks. Direct `eval` disables the analysis for the whole program while present. Exports, Script-root bindings, Annex B aliases, and `using` disposal remain observable even when they have no resolved AST reference.

## Example

Input:

```js
function self() { self() }
function a() { b() }
function b() { a() }
export {};
```

Output:

```js
export {};
```

## Supported

- Self-recursive and mutually recursive function declarations.
- References nested in blocks, arrows, function expressions, classes, and parameter defaults. The nearest registered function declaration owns each reference.
- ES modules, CommonJS, and local functions in Scripts. Script-root bindings remain visible to later scripts.
- Full compression and DCE-only mode.
- Reads, writes, exports, `using` disposal, and direct `eval` preserve live functions.
- Exact self-recursive variable initializers whose value is a `FunctionExpression` or `ArrowFunctionExpression`, including classic `for` initializers.

## Conservatively retained

- Mutual cycles between variable declarators, such as `const a = () => b(); const b = () => a()`.
- Recursive class cycles and mixed function/declarator/class cycles.
- Wrapped or arbitrary function-valued initializers, such as `const f = (effect(), () => f())`.
- Recursive declarators in `for-in` and `for-of` heads.
- Sloppy unhoisted Annex B block functions, whose runtime alias write is not represented by their block-scoped symbol.

## Performance

[CodSpeed's report for `e71c392`](#24125 (comment)) measured a 3.74% regression on `binder.ts`, where the analysis finds no dead graph. On `kitchen-sink.tsx`, removing 39 function declarations covering 25.3 kB of source early improved the minifier benchmark by 21.01% and the full pipeline by 8.76%. A separate 15-run Script/CommonJS corpus measured a 1.67% median increase overall, below the 2% acceptance threshold.

Verified with all-feature workspace tests, lint, rustdoc, formatting, AST generation, minsize and allocation snapshots, and the repeat-compression corpus.

Closes #13105
Closes #17364

Implemented with AI assistance (OpenAI Codex). The contributor remains responsible for reviewing, understanding, and submitting the changes under the repository's AI usage policy.