feat: generate record deconstructors alongside instantiators

[zantvoort]

Closes #295

What

The metamodel generators emit an Instantiator per record type, so record construction runs as generated code — but reading a record's components back out still went through reflective accessors. This completes the pair:

• Instantiator#deconstruct(T) — returns the canonical constructor arguments in declaration order as a freshly allocated array the caller may adjust and pass back to instantiate. The default returns null ("no generated deconstructor"), so instantiators generated before this change and types without generated support keep working unchanged through the reflective fallback.
• Both generators emit it: the Java annotation processor reads the record accessors, the KSP processor reads the data-class properties (backtick-quoted, so any property name works).
• Write-set rebuilds use it: key propagation and generated-key assignment (withComponent) now run the full deconstruct → adjust → instantiate round trip as generated code.

Why

• Native images: component reads as generated code are closed-world analyzable — no accessor reachability metadata to register, and no method-handle machinery in the write path.
• Cold start: generated reads start at full speed; the reflective path costs several hundred µs per write-set operation until the JIT catches up, which matters for short-lived processes.
• Warmed-JIT throughput is unchanged (measured); this is stated in Generate record deconstructors alongside instantiators for reflection-free rebuilds #295 so it is not mistaken for a performance item.

Testing

• storm-core: 2307 green after a clean rebuild — 45 test records regenerate with deconstructors and the write-set integration tests exercise the generated round trip.
• storm-h2: 158 green (write-set suite included).
• KSP verified end to end: the Kotlin benchmark project regenerates its instantiators with deconstructors, compiles, and runs the write-set graph insert with its key-count guards passing.
• Full reactor test-compile.