Overhaul agent quality — prompts, tools, config, compression

- Rewrite system prompt: structured sections, explicit tool descriptions
  with full SKILL.md descriptions, multi-agent awareness
- Add write_file skill for creating/modifying workspace files
- Per-template config passthrough: temperature, num_predict, context_size,
  compress settings, max_tool_rounds, max_response_lines
- Bump defaults: 1024 output tokens (was 512), 500-char deque (was 200),
  250-token summaries (was 150), compress threshold 16 (was 12), keep 8 (was 4)
- Cache compression by content hash — no redundant summarization
- Update all 5 templates with tuned settings per role

skills/write_file/SKILL.md

@@ -0,0 +1,17 @@
+---
+name: write_file
+description: Write content to a file in /workspace. Creates parent directories if needed. Use this to save scripts, reports, data, or any output you want to persist.
+parameters:
+  path:
+    type: string
+    description: Path to write (must be under /workspace)
+    required: true
+  content:
+    type: string
+    description: Content to write to the file
+    required: true
+  append:
+    type: boolean
+    description: If true, append to existing file instead of overwriting (default false)
+    required: false
+---