feat(memory+knowledge): add knowledge wiki system and Light Dream memory extraction

- Add knowledge/ directory structure and knowledge-wiki skill for structured knowledge accumulation
- Auto-inject MEMORY.md into system prompt with truncation (last 200 lines)
- Light Dream: extend flush_memory to extract long-term memories into MEMORY.md with date stamps
- Add mandatory knowledge auto-write rules in system prompt (no user confirmation needed)
- Expand MemoryManager.sync() to index knowledge/ files for vector search
- Update RULE.md template with workspace conventions and knowledge guidelines

skills/knowledge-wiki/SKILL.md

@@ -0,0 +1,90 @@
+---
+name: knowledge-wiki
+description: Manage the personal knowledge wiki. Use when the user shares articles, documents, or asks to organize knowledge; when a conversation produces insights worth preserving as structured knowledge; or when the user asks about the knowledge base.
+metadata:
+  cowagent:
+    always: true
+---
+
+# Knowledge Wiki
+
+Maintain a persistent, structured knowledge base in the `knowledge/` directory.
+
+## Core Operations
+
+### 1. Ingest — User shares an article, document, or resource
+
+1. Read and understand the source material
+2. Extract key facts, entities, concepts, and insights
+3. Create or update relevant pages:
+   - `knowledge/sources/<slug>.md` — source summary
+   - `knowledge/entities/<name>.md` — people, companies, projects mentioned
+   - `knowledge/concepts/<topic>.md` — new concepts or topics discussed
+4. Update `knowledge/index.md` — add one-line entry per new/updated page
+5. Append to `knowledge/log.md`
+
+### 2. Synthesize — Conversation produces valuable structured knowledge
+
+1. Create `knowledge/analysis/<slug>.md` with the structured analysis
+2. Update related entity/concept pages with cross-references
+3. Update `knowledge/index.md` and `knowledge/log.md`
+
+### 3. Query — User asks about accumulated knowledge
+
+1. Check `knowledge/index.md` (already in your context) for relevant pages
+2. Read specific pages with the `read` tool
+3. Supplement with `memory_search` if needed
+
+## Page Format
+
+```markdown
+# Page Title
+
+Content here. Reference other pages with markdown links:
+[Related Entity](../entities/related-entity.md)
+
+## Key Points
+
+- ...
+
+## Sources
+
+- [Source Title](../sources/source-slug.md)
+```
+
+## Index Format (`knowledge/index.md`)
+
+Flat list, one line per page: `[Title](path) — one-line summary`. No tables, no emoji, no template headers.
+
+```markdown
+# Knowledge Index
+
+## Concepts
+- [Topic Name](concepts/topic-name.md) — one-line description
+
+## Sources
+- [Article Title](sources/article-slug.md) — one-line summary
+
+## Entities
+- [Entity Name](entities/entity-name.md) — one-line description
+
+## Analysis
+- [Analysis Title](analysis/analysis-slug.md) — one-line summary
+```
+
+## Log Format (`knowledge/log.md`)
+
+Append-only, newest at bottom:
+
+```markdown
+## [2026-04-09] ingest | DeepSeek-R1 Deploy Guide
+## [2026-04-09] synthesize | Memory System Design Analysis
+```
+
+## Guidelines
+
+- **File naming**: lowercase kebab-case (e.g. `machine-learning.md`)
+- **One topic per page**: link between pages rather than duplicating
+- **Update, don't duplicate**: if a page exists, update it
+- **Index is mandatory**: always update `knowledge/index.md` after any change
+- **Be concise**: capture essence, not copy entire sources