docs: generalize semantic deduplication as a consistent cross-document convention

[Copilot]

Semantic deduplication existed as an ad-hoc note in the strategy doc. This propagates it as a coherent, scoped, human-guided convention across all relevant docs without adding automation or over-engineering the concept.

Changes

docs/advanced_memory_strategy.md

• Replaced the hard "80% or more" threshold in §5.3 with a forward reference to the new similarity table
• Added an optional subsection with a three-tier threshold table (≥0.86 / 0.55–0.85 / <0.55), scoped-comparison framing, type-aware exception, and preserve-original enrichment rule
• Thresholds explicitly framed as a refinement on top of writing discipline, not a gate

docs/memory_example.md

• Added a short "Optional semantic deduplication" section with a concrete myapp/architecture example: compare in-scope, enrich instead of duplicating, keep separate when types differ

docs/deduplication.md (new)

• Compact standalone reference: why dedup matters, scoped comparison, threshold table, enrich vs. create, type-aware exception, human-first rule
• Linked from all three other docs

ros2-architecture-context.instructions.md (new)

• Agent instruction file for ROS 2 / MemPalace workflows
• Persistence section includes explicit threshold table, wing+room scope restriction, type-aware exception, and preserve-original enrichment guidance
• Context-gathering order and fallback behavior (memory unavailability never blocks a task)