Engine: CEL standard function library (string/math/list/map/conversions/timestamp/duration)

[rrrodzilla]

Workstream: Engine · Part of #89

Context

The CEL standard function/operator library over DynamicValue, plugged into the evaluator core (#108).

Scope

• String functions (size, contains, startsWith, endsWith, matches, ...).
• Numeric/math and list/map operations.
• Type conversions (int/uint/double/string/bytes/bool/timestamp/duration) and dyn/type ops.
• Timestamp/duration functions + arithmetic (ties to Type: duration (records retention / TTL / SLA) + timestamp arithmetic #96/Type/semantics: CEL timestamp operations (tz-aware accessors, overflow rules) #101): getFullYear, getHours(tz), …, timestamp ± duration.
• Selected extensions only as needed (strings_ext, math_ext, encoders_ext); log any deliberately-unimplemented functions (no silent gaps).

Acceptance

• Passes the string, integer_math, fp_math, conversions, timestamps (+ chosen *_ext) subset sections of Spike: measure pure-Rust CEL conformance against the official cel-spec suite #90.

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Dependencies: Blocked by #108 (evaluator core). Required (with the evaluator) by the capabilities #92/#93/#94. Hard.

[rrrodzilla]

Landed in 62b4419 — feat(cel): add standard function library (#109), plus follow-ups 8f54e4f (i64::MIN parse, #114) and 9550c88 (two-variable comprehension macros, #113). String/math/list/map/conversion/timestamp/duration built-ins are in. Closing; code merged on dev.