fix(angular): fix 5 compiler divergences from Angular reference

[Brooooooklyn]

1. (High) @let self-reference: mark name as declared AFTER transforming
   the declaration op, so self-references like @let x = x + 1 are
   replaced with undefined — matching Angular's backward walk.

2. (Medium) @for invalid-shape recovery: return None when expression
   parsing fails or track is missing, matching Angular which returns
   null node instead of synthesizing a broken ForLoopBlock.

3. (Medium) @if invalid main-parameter recovery: only push the main
   branch (and @else if branches) when the expression parses
   successfully, matching Angular's conditional push.

4. (Medium) @switch invalid parameter count: parse the first parameter
   when present (even with extra params), only use empty binding when
   there are no parameters — matching Angular's createSwitchBlock.

5. (Low) Reify conditional contract: replace panic with
   OxcDiagnostic::error for missing processed expression, matching the
   StoreLet precedent in the same file and the project convention of
   diagnostics over panics.

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

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Note

Medium Risk
Changes affect control-flow block AST emission and @let reference rewriting, which can alter generated code and error-recovery behavior across templates. Risk is moderated by added conformance tests and diagnostics replacing panics.

Overview
Aligns several template-compiler behaviors with Angular’s reference implementation, primarily around control-flow and error recovery.

@let handling now treats the declaration op itself as not yet declared, so self-references like @let x = x + 1 are rewritten to undefined (matching Angular’s backward walk). Control-flow transforms now skip emitting @for nodes when parameter parsing fails or when track is missing, skip pushing @if/@else if branches when the condition expression didn’t parse, and adjust @switch to always parse the first parameter when present even if extra params exist.

Reify’s Conditional op no longer falls back to test/null; it emits a diagnostic and drops the stmt if the processed condition is missing. Adds/updates integration and R3-transform tests plus a snapshot to lock in the new conformance behavior.

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[Brooooooklyn]

• fix(angular): fix 5 compiler divergences from Angular reference #34 👈 (View in Graphite)
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