🏗️ 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/tome/README.md

@@ -0,0 +1,27 @@
+# 📖 Tome
+
+Knowledge layer for agent-managed projects. Tome gives agents a structured way to navigate, curate, and maintain a project's knowledge base — CLAUDE.md files, topic docs, domain maps.
+
+**Opt-in.** Install the plugin, then run `/tome:init` in your project to scaffold the knowledge structure. Without init, the skills are available but have nothing to navigate.
+
+## Skills
+
+| Skill | Description |
+|-------|-------------|
+| `navigate` | Find the right CLAUDE.md or topic doc for a given question. Entry point for knowledge lookups. |
+| `curate` | Maintain and improve knowledge files — fill gaps, fix stale content, restructure. |
+| `check` | Verify knowledge-layer health: stale refs, missing docs, broken links. |
+| `handoff` | Prepare knowledge for a session transition or successor agent. |
+| `init` | Scaffold a project's knowledge structure from scratch. |
+
+## Installation
+
+Add `tome` to `enabledPlugins` in `.claude/settings.json` (official) or `.claude/settings.local.json` (shadow):
+
+```json
+{
+  "enabledPlugins": ["tome@reliquary"]
+}
+```
+
+Pairs well with `spire` — Igor and adepts can use tome skills when available, but don't require them.