refactor: merge attention-filters into check-phase skill

Consolidate the attention-filters skill (122 lines) into check-phase,
reducing check-phase from 234 to 110 lines. Removed verbose bash code
blocks, 30-line consolidated output example, re-check protocol (belongs
in act-phase), and motivational section. Updated all references in
README, plugin.json, using-archeflow, and colette-bridge.

README.md

@@ -164,7 +164,6 @@ ArcheFlow ships with 24 skills organized by function.
 | Skill | Description |
 |-------|-------------|
 | `archeflow:shadow-detection` | Quantitative dysfunction detection and automatic correction |
-| `archeflow:attention-filters` | Context optimization per archetype -- each agent gets only what it needs |
 | `archeflow:convergence` | Detects convergence, stalling, and oscillation in multi-cycle runs |
 | `archeflow:artifact-routing` | Inter-phase artifact protocol -- naming, storage, routing, archiving |
 
@@ -358,7 +357,6 @@ archeflow/
 │   ├── check-phase/             #   Check protocols
 │   ├── act-phase/               #   Act phase decision logic
 │   ├── shadow-detection/        #   Dysfunction detection
-│   ├── attention-filters/       #   Context optimization
 │   ├── convergence/             #   Cycle convergence detection
 │   ├── artifact-routing/        #   Inter-phase artifact protocol
 │   ├── process-log/             #   Event-sourced JSONL logging