Pure-call summaries and member-write hazards encoded semantic states through nested `Option` values and independent bitflags. Reviewers had to reconstruct which combinations were valid and which implications producers must maintain.

This introduces `FunctionSummary` for reusable call proofs and an ordered `MemberWriteEffect` for `None < Hazard < MayMutatePrototype`. Prototype mutation is therefore hazardous by construction, the removed bitflag dependency is no longer needed, and producers and consumers share named contracts. Behavior is unchanged relative to #24636.

The PR tip passed the full `oxc_minifier` suite independently. The completed stack also passed clippy with warnings denied, formatting, minsize and allocation regeneration, and `just ready`.

## Stack

1. #24636 — function-summary correctness
2. **#24637 — explicit symbol effect types**
3. #24638 — grouped reference counts
4. #24639 — merged persistent metadata
5. #24640 — SymbolState facade

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

`SymbolValue` exposed three related counters directly, so every consumer had to coordinate read, write, and member-write-target invariants itself.

This groups them in `ReferenceCounts` and exposes factual queries such as `has_single_read` and `has_only_member_write_target_reads`. The existing 48-byte `SymbolValue` layout is preserved, and the refactor does not change minified output.

The PR tip passed the full `oxc_minifier` suite independently. The completed stack also passed clippy with warnings denied, formatting, minsize and allocation regeneration, and `just ready`.

## Stack

1. #24636 — function-summary correctness
2. #24637 — explicit symbol effect types
3. **#24638 — grouped reference counts**
4. #24639 — merged persistent metadata
5. #24640 — SymbolState facade

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

Pure-call summaries and member-write effects used separate sparse hash maps even though both are keyed by `SymbolId` and remain valid across peephole iterations.

This stores both values in one `PersistentSymbolMetadata` entry. Summary replacement and monotone member-effect strengthening remain independent, and clearing a dynamic-binding summary updates an existing entry without allocating or discarding its member effect.

The regenerated allocation snapshot records fewer system allocations: checker 155→152, pdf 2469→2467, antd 1044→1038, and kitchen-sink 1872→1867. `minsize.snap` remains byte-identical.

The PR tip passed the full `oxc_minifier` suite independently. The completed stack also passed clippy with warnings denied, formatting, minsize and allocation regeneration, and `just ready`.

## Stack

1. #24636 — function-summary correctness
2. #24637 — explicit symbol effect types
3. #24638 — grouped reference counts
4. **#24639 — merged persistent metadata**
5. #24640 — SymbolState facade

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

`MinifierState` separately exposed dense per-pass values, sparse persistent metadata, and optional reachability state even though all three are indexed by semantic symbols. Its private-member stack also used symbol terminology despite storing names rather than `SymbolId`s.

This introduces a `SymbolState` facade that documents the three storage lifecycles and forwards their operations while leaving the reachability algorithm in its dedicated module. The class-local tracker is renamed around private-member usage so it cannot be confused with semantic symbol state.

The PR tip passed the full `oxc_minifier` suite independently. The completed stack also passed clippy with warnings denied, formatting, minsize and allocation regeneration, and `just ready`.

## Stack

1. #24636 — function-summary correctness
2. #24637 — explicit symbol effect types
3. #24638 — grouped reference counts
4. #24639 — merged persistent metadata
5. **#24640 — SymbolState facade**

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

### 💥 BREAKING CHANGES

- 54cc121 ast: [**BREAKING**] Split `MetaProperty` into `ImportMeta` and
`NewTarget` (#24557) (camc314)

### 🚀 Features

- 4c71560 parser: More friendly error for spread element in dynamic
imports (#24705) (sapphi-red)
- 7b045cd minfier: Drop last break from last switch case (#24673)
(Armano)
- 7d3c178 minifier: Remove unreachable recursive functions (#24125)
(Dunqing)
- 94f99b3 ast: Allow `NONE` to be passed to AST builder methods where
`Option<ArenaVec>` is expected (#24629) (overlookmotel)
- 77230c5 ast: Accept arrays for `ArenaVec` params of AST builder
methods (#24621) (overlookmotel)
- f08b152 allocator: Implement `FromIn` for array to `Vec` conversion
(#24620) (overlookmotel)
- 2338c13 track-memory-allocations: Track heap deallocs, alloc bytes,
and peak growth (#24619) (Boshen)
- 7aa4739 syntax,transformer: Move JSX entity decoder to `oxc_syntax`
(#24617) (camc314)
- 2b097c4 str: Export `Str` as `ArenaStr` (#24604) (overlookmotel)
- 3acf4c1 minifier: Expand switch optimiation to remove empty cases
(#24520) (Armano)
- 129b759 parser: Improve diagnostics for unparenthesized LHS on
exponential expr (#24569) (camc314)
- 4d0c601 minifier: Fold arithmetic over undefined and null operands
(#24485) (Dunqing)
- 91541dd minifier: Drop empty switch statements  (#24527) (Armano)
- d05224d ast_visit: Generate VisitJs visitor that skips TypeScript
type-space (#24499) (Boshen)
- 3d22307 parser: Add `ParseOptions::enable_ident_hashes` (#24491)
(Boshen)

### 🐛 Bug Fixes

- 64c2241 minifier: Align class heritage removal with assumptions
(#24533) (Dunqing)
- 48b59f4 parser: Span ambient generator diagnostics (#24711) (camc314)
- e750a82 ecmascript: Fix false negative for may_have_side_effects on
dynamic property access (#24709) (sapphi-red)
- f145d73 minifier: Guard reordered identifier reads (#24698) (Dunqing)
- a2ef382 isolated-declarations: Reject `window.Symbol` as global symbol
reference (#24689) (camc314)
- b1bcf72 minifier: Invalidate facts for redeclared bindings (#24658)
(Dunqing)
- 921b834 minifier: Don't treat a conditionally-assigned var as
write-once (#24650) (Dunqing)
- 061af1f minifier: Avoid stale pure function summaries (#24636)
(Dunqing)
- 40c2f43 allocator: `Vec::from_array_in` do not allocate zero-length
array (#24628) (overlookmotel)
- 70994ae codegen: Preserve comments before expression operands (#24510)
(Dunqing)
- 7b4baff parser: Reject new import member access (#23459) (camc314)
- 128b385 minifier: Clippy warning with no-debug-assertions (#24547)
(camc314)
- 8421feb parser: Use first `as` span for imported name (#24537)
(leaysgur)
- c517aa0 parser: Reject invalid accessor assertions (#24504) (camc314)

### ⚡ Performance

- 884d9eb parser: Pre-size cover-grammar assignment target buffers
(#24683) (Boshen)
- d3f07a0 diagnostics: Box OxcDiagnosticInner to reduce binary size
(#24665) (Boshen)
- bcc9de0 parser: Defer diagnostic creation until parse exit (#24663)
(Boshen)
- c35d8ab allocator: Mark `ReplaceWith` panic path cold (#24515)
(camc314)
- ba65790 semantic, allocator: Branchless `clone_in` for semantic IDs
(#24564) (overlookmotel)
- 747feec parser: Build AST nodes with the AST builder instead of
cloning (#24540) (Boshen)
- ba35a0d react_compiler: Use IndexVec for dense id-keyed maps (#24549)
(Boshen)
- b685062 react_compiler: Keep small hot-path collections inline
(#24514) (Marius Schulz)
- a149e95 transformer: Outline rare expression exits (#24512) (camc314)
- 7808a6e react_compiler: Make aliasing effects cheap to intern and
clone (#24506) (Marius Schulz)
- 3a36f2a react_compiler: Store AbstractValue reasons as a u16 bitmask
(#24480) (Boshen)
- 1c96753 react_compiler: Use FxHashMap for the lookup-only aliasing
node map (#24490) (Boshen)

Co-authored-by: Cameron <[email protected]>