Remove dead compiler block-state caches

[irimias57]

Created from 475-remove-dead-compiler-block-state-caches.md.

TODO: Remove Dead Compiler Block-State Caches

Problem Description

CompilationContext still carries activeBlockDepths and seven inside...Block booleans for module, function, generic,
loop, condition, constants, and map blocks. The shared block-stack helpers update all of these fields on every block
push and pop, and context construction derives them from blockStack.

These caches were introduced for direct block-placement checks, but no production consumer reads them anymore. Current
loop and map consumers use the narrower activeLoopBlocks and activeMapBlock caches instead. The dead fields now add
state that must stay synchronized, broaden the compiler context contract, and preserve tests for behavior that no
runtime compiler path needs.

Proposed Solution

Remove activeBlockDepths and all seven legacy inside...Block booleans from the compiler context and its construction
and mutation helpers. Simplify block pushes and pops so they maintain only the ordered blockStack and the actively
consumed loop/map caches.

Keep activeLoopBlocks and activeMapBlock. They provide direct access to data used by semantic reference resolution,
stack analysis, and code generation and are not part of this cleanup.

Anti-Patterns

• Do not retain aliases, optional fallback fields, or compatibility accessors for the removed caches.
• Do not replace the dead fields with repeated blockStack scans when no consumer needs the information.
• Do not remove blockStack, activeLoopBlocks, or activeMapBlock as part of this focused cleanup.
• Do not preserve tests whose only purpose is verifying updates to removed state.

Implementation Plan

Step 1: Narrow The Compilation Context

• Remove activeBlockDepths and the seven inside...Block properties from CompilationContext.
• Remove the same fields from context override/helper types and test fixtures.
• Keep the ordered block stack and actively consumed loop/map cache types unchanged.

Step 2: Simplify Context Construction

• Stop creating and deriving block-depth counts in createCompilationContext.
• Narrow getBlockState to derive only activeLoopBlocks and activeMapBlock, or remove the helper if its remaining
  work is clearer inline.
• Remove override behavior that exists solely for the deleted caches.

Step 3: Simplify Block Mutation

• Remove depth increments and decrements from pushBlock and popBlock.
• Delete updateBlockContextFlag and its block-type switch.
• Continue maintaining activeLoopBlocks and activeMapBlock exactly as current consumers require.

Step 4: Update Tests And Fixtures

• Delete assertions for the removed boolean flags and depth counts.
• Update manually constructed compiler contexts in stack-analyzer and compiler tests.
• Retain nested-loop and map coverage that verifies the live caches and ordered block stack.

Validation Checkpoints

• rg -n "activeBlockDepths|inside(Module|Function|Generic|Loop|Condition|Constants|Map)Block" packages/compiler
• npx nx run @8f4e/language-spec:typecheck
• npx nx run @8f4e/semantic-utils:test
• npx nx run @8f4e/semantic-utils:typecheck
• npx nx run @8f4e/stack-analyzer:test
• npx nx run @8f4e/stack-analyzer:typecheck
• npx nx run @8f4e/semantic-reference-resolver:test
• npx nx run @8f4e/wasm-codegen:test
• npx nx run @8f4e/compiler:test
• npx nx run @8f4e/compiler:typecheck

Success Criteria

• CompilationContext contains no activeBlockDepths or inside...Block compatibility fields.
• Block push/pop operations no longer update unused depth or boolean state.
• Context construction no longer derives unused block-state caches.
• blockStack, activeLoopBlocks, and activeMapBlock behavior remains covered and unchanged.
• Compiler package tests and typechecks pass without compatibility aliases or fallback reads.

Affected Components

• packages/compiler/packages/language-spec/src/semantic.ts - narrow CompilationContext.
• packages/compiler/packages/sub-program/packages/semantic-utils/src/createCompilationContext.ts - remove dead cache construction.
• packages/compiler/packages/sub-program/packages/semantic-utils/src/blockStack.ts - remove dead cache synchronization.
• packages/compiler/packages/sub-program/packages/semantic-utils/src/blockStack.test.ts - remove obsolete assertions and retain live-cache coverage.
• packages/compiler/packages/sub-program/packages/stack-analyzer/src/analyzeInstruction.test.ts - update manually constructed context fixtures.

Risks & Considerations

• Hidden consumers: Run a repository-wide identifier search before deletion; typechecking should catch structural
  context consumers that are not found by the initial source audit.
• Nested loops: Preserve activeLoopBlocks nesting behavior while simplifying the generic block-state machinery.
• Map lifecycle: Maps are non-nestable by placement rules, but activeMapBlock must still be cleared at the same
  point during block closure.
• No compatibility burden: These fields are compiler-internal and unused, so remove them directly rather than
  deprecating them.

Related Items

• Related: docs/todos/archived/409-track-block-context-flags-during-stack-analysis.md
• Related: docs/todos/archived/463-refactor-stack-analyzer-to-return-fact-report.md