fix(angular): fix 6 compiler divergences from Angular reference

[Brooooooklyn]

1. viewport({trigger: ...}) now keeps empty options object (was dropping it)
2. Timer delays preserve fractional precision (u32 -> f64, e.g. 1.5ms)
3. Pipe detection in @for track now traverses all AST expression types
4. hover/interaction triggers enforce max 1 parameter; never removed from on-triggers
5. @for let assignment a=b=c correctly rejected (split instead of splitn)
6. @for expression parse failure no longer emits extra missing-track error

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

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Note

Medium Risk
Touches template parsing and IR/reify generation for @defer and @for, so behavior changes may affect emitted output and error reporting across many templates despite being targeted compatibility fixes.

Overview
Aligns @defer trigger handling with Angular by preserving fractional timer delays end-to-end (u32 -> f64), keeping empty viewport options objects for viewport({trigger: ...}), and tightening trigger validation (enforce max 1 parameter for hover/interaction, and reject never as an on trigger).

Improves @for parsing/validation to match Angular: adds an expression_parse_failed flag to avoid emitting an extra missing-track error on expression parse failures, rejects malformed let assignments like a=b=c, and expands pipe detection in track expressions to traverse more AST node types. Adds new e2e fixtures covering defer edge cases (empty viewport options + fractional timer durations).

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[Brooooooklyn]

• fix(angular): fix 6 compiler divergences from Angular reference #31 👈 (View in Graphite)
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