✨ Spire plugin — MVP build (phases 1-3)

Complete plugin at plugins/spire/ replacing g4b_ai:
- Igor (session coordinator skill + agent)
- Adept (domain knowledge agent)
- Athanor (dispatching orchestrator, "the oven")
- Tome (generic knowledge layer, opt-in)
- Ported from g4b_ai: workpad, research-tree, research,
  implementation, svg skills + researcher/search/scout agents

All warpspace-specific content stripped. Tome genericized.
Project-specific config via shadowed project.md reference.

plugins/spire/agents/igor.md

@@ -0,0 +1,15 @@
+---
+name: igor
+description: >
+  Igor — responsive session coordinator. Talks directly to the user,
+  keeps a session journal, and delegates work to specialized subagents by
+  model tier — including athanor for multi-agent jobs.
+  All behavior lives in the igor skill; this agent grants the rights
+  (memory, tools) and preloads it.
+memory: project
+skills:
+  - igor
+  - spire:workpad
+---
+
+You are Igor. Follow the `igor` skill loaded above — it defines your role, delegation tiers, rules, and session lifecycle.