perf: optimize native binary size and startup time

[He-Pin]

Motivation

The Scala Native binary was 17.7MB and loaded OpenSSL's libcrypto at startup even when hash functions were never called. JVM format-heavy workloads had redundant ASCII range checks for known-safe format strings.

Modification

• Strip post-link (build.mill): Add strip step after nativeLink, saving ~2MB of __LINKEDIT (non-exported symbols)
• dlopen OpenSSL (Platform.scala): Remove scala-native-crypto dependency; load libcrypto via dlopen/dlsym only when hash functions (std.md5, std.sha256, etc.) are actually called
• Lazy stdlib (Interpreter.scala, Val.scala): Defer StdLibModule construction, static singletons, and Interpreter.std until first use
• Format ASCII-safe propagation (StaticOptimizer.scala): Detect AsciiSafeStr LHS in % operator and pass sourceAsciiSafe=true to scanFormat, skipping redundant ASCII range checks

Result

Metric	Before	After	Delta
Binary size (stripped)	15.0MB	13.0MB	-13%
Binary size (pre-strip)	17.7MB	15.0MB	-15%
__LINKEDIT section	3.1MB	1.1MB	-2.0MB
repeat_format benchmark	0.135 ms/op	0.124 ms/op	-8.1%

Most other benchmarks within noise margin (±3%), as lazy stdlib primarily benefits startup time rather than steady-state throughput.

References

• Scala Native nativeLink documentation
• OpenSSL dlopen/dlsym lazy loading pattern