Migrate Worker memory ownership to Strata

[zekageri]

Summary

• bump Worker to v0.2.0 and require Strata v0.1.1
• replace WorkerStackType with the shared Strata::MemoryPolicy / Strata::Placement vocabulary
• add optional per-job and cleanup-task stack placement overrides with std::nullopt inheritance
• replace Worker-specific task allocation, PSRAM capability handling, queue creation, and recursive mutex allocation with Strata FreeRTOS ownership primitives
• route job records, registry/completion container backing, cleanup queue storage, Worker implementation ownership, and event callback ownership through Strata
• keep Worker’s external cleanup lifecycle and add task publication/deletion handoff guards around Strata task owners
• change result messages from owning std::string to static const char *
• report requested placement separately from observed Strata region in job and cleanup diagnostics
• add CI audits that prevent direct allocation / FreeRTOS creation paths from returning
• update examples and docs, including migration mapping from Worker v0.1.0

Compatibility

This intentionally establishes a clean v0.2.0 API rather than carrying Worker-specific compatibility aliases:

• WorkerStackType::Auto -> Strata::Placement::PreferExternal
• WorkerStackType::Internal -> Strata::Placement::Internal
• WorkerStackType::Psram -> Strata::Placement::RequireExternal
• defaultStackType -> memory.taskStack
• stackType -> optional stackPlacement
• WorkerResult::message is now const char *

Worker remains responsible for jobs, callbacks, cooperative cancellation, sleep/wait behavior, concurrency, and cleanup orchestration. Strata now owns allocation placement and low-level task/queue/mutex storage.

Validation

Validated on PR head 28b93811524f5ff9491137931af04f28f2fb6728:

• advisory lint: passed
• allocation/source audit: passed
• Arduino CLI examples: ESP32, ESP32-S3, ESP32-C3, ESP32-P4 all passed
• PIOArduino examples: ESP32, ESP32-S3, ESP32-C3, ESP32-P4 all passed

The TaskCleanupSentinel example now compiles under PreferExternal general allocation and task-stack policies. Source audits reject direct ESP-IDF heap capabilities, raw new/delete, and direct dynamic task/queue/semaphore creation from production Worker sources.