feat: improve skill descriptions from PR #9 (selective merge)

Cherry-pick description improvements and allowed-tools fixes from @popey's
PR #9, while preserving reference documentation in skills that serve as
templates (audit-agents-skills, ccboard, design-patterns).

Co-Authored-By: Alan Pope <alan@popey.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/memory/icm-session-starter.md

@@ -0,0 +1,76 @@
+# ICM Session Starter
+> Paste this at the beginning of any Claude Code session to activate ICM context.
+> Requires ICM installed and configured: `brew tap rtk-ai/tap && brew install icm`
+> then `icm init --mode mcp && icm init --mode hook && icm init --mode skill`
+
+---
+
+# Context — ICM (Infinite Context Memory) active in this session
+
+ICM is installed and configured on this machine. Use it to store and retrieve persistent
+memory across sessions, bypassing context window limits.
+
+## Available MCP tools
+
+The `icm` MCP server is running. You have access to 22 `icm_*` tools for storing,
+recalling, and managing persistent memory.
+
+**Direct CLI** (via Bash if needed):
+
+```bash
+# Store a memory
+icm store --topic "<project-slug>" --content "<fact>" --importance high|medium|low|critical
+
+# Recall by semantic query
+icm recall "<natural language query>"
+
+# Inspect
+icm stats          # count, topics, avg weight
+icm topics         # list all topics
+icm list           # list recent memories
+
+# Manage
+icm forget <id>    # delete by ID
+icm decay          # apply temporal decay
+icm prune          # remove low-weight entries
+```
+
+**Important (v0.5.0 syntax)**:
+- `--importance` is an enum: `critical / high / medium / low` — not a float
+- No `memory` subcommand — use `icm store`, `icm recall` directly
+- Permanent knowledge graph: `icm memoir` (separate layer, no decay)
+
+## Slash commands
+
+- `/recall <query>` — search ICM memory
+- `/remember <content>` — store a memory in ICM
+
+## How memories work
+
+Two layers:
+- **Memories** (episodic): timestamped entries with temporal decay based on importance.
+  `critical` importance never decays. `low` fades over time.
+- **Memoir** (semantic): permanent knowledge graph with typed relations
+  (`depends_on`, `contradicts`, `superseded_by`, `part_of`, and 5 others).
+
+Search is hybrid: BM25 full-text (30%) + vector similarity (70%).
+
+A `PostToolUse` hook runs automatically — every N tool calls, ICM extracts context
+and stores it without any explicit action from you.
+
+## Suggested usage in this session
+
+```bash
+# At session start — recall relevant context
+icm recall "<current feature or topic>"
+
+# When making a key decision
+icm store --topic "<project>" --content "<decision and rationale>" --importance high
+
+# For permanent architectural facts
+icm memoir add-concept -m "<project>" -n "<concept>"
+```
+
+## DB location
+
+`~/Library/Application Support/dev.icm.icm/memories.db`