F22-08: Memory leak detection (valgrind/miri)

[aram-devdocs]

Parent: #137

Run miri and/or valgrind to detect memory leaks and use-after-free across the engine.

Acceptance Criteria

• Miri runs over non-GL Rust tests (GL is not miri-compatible)
• Valgrind or heaptrack run over integration tests
• Zero memory leaks reported in steady-state operation
• Any leaks found are fixed and documented
• Added to CI on a scheduled (not per-PR) basis to manage runtime cost

[aram-devdocs]

The underlying leak is fixed in #705: dynamic component storage was keyed by entity index alone, so despawn never freed slots and a recycled index could read a dead entity's data. It's now generation-checked with a per-context purge on despawn (five Rust regression tests + a security-auditor pass), and the previously-skipped C# Despawn_10k_Entities_Cleans_Up_Component_Storage test is un-skipped. The valgrind/miri leak-detection lane from this issue's scope is still open.

[aram-devdocs]

Closing as superseded by the ENG2 v2 rebuild program.

• Replacement: ENG2-P3-08 ((ENG2-P3-08?)) — leak canary CI
• Runbook: docs/src/runbook/phase-index.md · Master: ENG2: GoudEngine v2 Rebuild — Master Tracking #810

Nothing was dropped — the v2 roadmap was designed from a full-engine code audit that covers this issue's area. If you believe scope was lost, comment on #810.