🏗️ Extract tome from spire into standalone plugin

Tome is opt-in per project — each project declares its own knowledge
management approach. Spire retains a small knowledge-awareness skill
that explains what tome does and provides a fallback strategy for
projects without it.

- New plugins/tome/ with own manifests, README, all 5 sub-skills
- Spire keeps skills/knowledge/SKILL.md as awareness stub
- Updated all READMEs and marketplace JSONs
- tome: namespace refs now correct (tome is its own plugin)

plugins/spire/skills/knowledge/SKILL.md

@@ -0,0 +1,54 @@
+---
+name: knowledge
+description: >
+  Knowledge management awareness — explains how a project's knowledge base works,
+  how to navigate it, and what to do when the tome plugin isn't installed. Each
+  project declares its own approach in project.md.
+---
+
+# Knowledge Management
+
+Spire agents (Igor, adepts, athanor) need to orient themselves in a project's knowledge base. How that knowledge is structured varies per project.
+
+## How projects declare their knowledge approach
+
+The project's `project.md` (loaded by Igor's skill and by athanor) should describe:
+
+- Where authoritative docs live (CLAUDE.md files, topic docs, wiki/)
+- How to navigate them (tome plugin, direct file reads, AGENTS.md routing tables)
+- What the entry point is (root CLAUDE.md, boot.md, AGENTS.md)
+
+## When the tome plugin is installed
+
+If the project has `tome@reliquary` enabled:
+
+- Use `/tome:navigate` before substantial work in an unfamiliar area
+- Use `/tome:check` to verify knowledge-layer health after structural changes
+- Use `/tome:curate` for knowledge maintenance
+- Use `/tome:handoff` when transitioning between sessions or agents
+
+Tome provides structured navigation (wiki/, NAV files, boot.md) and automated curation methods. It's the full-featured path.
+
+## When tome is not installed (fallback)
+
+Most projects work fine without tome. The fallback strategy:
+
+1. **Read the root CLAUDE.md / AGENTS.md** — this is always the entry point
+2. **Follow @-includes and links** — CLAUDE.md files reference each other; follow the chain relevant to your task
+3. **Check for module-level CLAUDE.md** — many projects have per-module docs (`src/foo/CLAUDE.md`)
+4. **Use `find` or `glob`** for `**/CLAUDE.md` to discover what documentation exists
+5. **Read topic docs** if they exist (`docs/topics/`, `docs/`, or similar)
+
+The fallback is manual but sufficient. Tome automates what fallback does by hand.
+
+## Installing tome
+
+To add tome to a project:
+
+```json
+{
+  "enabledPlugins": ["tome@reliquary"]
+}
+```
+
+Then run `/tome:init` to scaffold the knowledge structure. This is a one-time setup that creates the wiki/, boot.md, and folder navigation. See the tome plugin's README for details.