llm: drop model/agent scope matching; add instance-wide compaction model picker

Remove the scope system end-to-end (llm_models.scope column, agent meta
scope field, scope-based tier in model selection, UI checkboxes/pills):
it was only a soft ranking hint, had drifted (6 UI scopes vs 3 used by
agents, 'general' not even selectable) and duplicated what strength
already decides. Strength stays the single AUTO-selection axis.

Compaction: the summary model is now pickable from the Settings page
via a new PropertyType::LlmModel config property (registry key
compaction_model), instance-wide and live (no restart). Fallback chain:
explicit pick -> compaction.strength from config.yml -> priority order;
a deleted configured model degrades to AUTO. ContextCompactor reads the
key at compact time through GlobalConfigManager.

agents/business-analyst/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Pass the idea, the draft business plan, and any market/competitor evidence you have. Specify an output path/dir for the critique report. The more evidence you provide, the sharper the critique — missing evidence is flagged as open questions, not guessed.",
   "type": "task",
-  "scope": "reasoning",
   "strength": "high",
   "icon": "icon.png"
 }

agents/code-explorer/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Give it a concrete question or area to investigate (a bug, a module, an architecture concern). It writes a Markdown report to data/explorer/ and returns a summary. It never edits code or plans work.",
   "type": "task",
-  "scope": "reasoning",
   "strength": "high",
   "icon": "icon.png"
 }

agents/generalist/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Hand it a fully-specified task: what to change and where. It executes but does not plan, decide scope, or QA its own output, so be explicit about the desired outcome.",
   "type": "task",
-  "scope": "general",
   "strength": "average",
   "icon": "icon.png"
 }

agents/project-coordinator/meta.json

@@ -13,7 +13,6 @@
     }
   },
   "type": "chat",
-  "scope": "reasoning",
   "strength": "average",
   "inject_memory": ["user-memory/index.md", "shared-memory/index.md", "__PROJECT_ROOT__/SKALD.md"],
   "icon": "icon.png"

agents/researcher/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Pass a specific research question; optionally hint at depth (how many sources) or a time horizon. Optionally specify an output file/dir in the prompt to write the report outside the default `data/research/`. Returns a path + one-line summary, also saved to the scratchpad.",
   "type": "task",
-  "scope": "general",
   "strength": "average",
   "icon": "icon.png"
 }

agents/software-architect/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Describe the change or feature and the relevant part of the codebase. It produces an implementation plan and may delegate the actual edits to software-engineer. Use it when the work needs design before coding.",
   "type": "task",
-  "scope": "reasoning",
   "strength": "very_high",
   "icon": "icon.png"
 }

agents/software-engineer/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Give it a clear, scoped implementation task: which files or behaviour to change and the intended result. Best for executing an already-decided design — pair with software-architect when the approach is still open.",
   "type": "task",
-  "scope": "coding",
   "strength": "high",
   "icon": "icon.png"
 }

agents/spec-writer/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Provide the idea, the goals, and any constraints. It researches and produces a thorough Markdown spec document. It never writes implementation code — use it before building, not during.",
   "type": "task",
-  "scope": "reasoning",
   "strength": "high",
   "icon": "icon.png"
 }

agents/tech-lead/meta.json

@@ -14,7 +14,6 @@
   },
   "instructions": "Point it at project documentation or high-level requirements (and the working directory if relevant). It decomposes the work, sequences tasks by dependency, and orchestrates software-architect/software-engineer to deliver. Best for whole-project builds, not single edits.",
   "type": "task",
-  "scope": "reasoning",
   "strength": "very_high",
   "icon": "icon.png"
 }