feat(mem0-plugin): power-user skills + expanded mem0.md config (Tier 8)

Power-user tier:
- /mem0:remember: quick-add with auto-classification, infer=False, confidence=1.0
- /mem0:forget: search-confirm-delete flow with numbered list
- /mem0:pin: mark memories as pinned via metadata update
- /mem0:peek: compact one-liner search results
- parse_mem0_config.py: expanded to parse ## Search, ## Categories, ## Identity
- on_session_start.sh: inject mem0.md project config into session context

mem0-plugin/skills/mem0-forget/SKILL.md

@@ -0,0 +1,61 @@
+---
+name: mem0-forget
+description: >
+  Delete memories by search query or memory ID. Shows matches for confirmation
+  before deleting. Safe — always confirms before destructive action.
+  TRIGGER: user runs /mem0:forget <query>, or says "forget this", "delete memory",
+  "remove that memory about X".
+---
+
+# Mem0 Forget
+
+Delete specific memories from mem0.
+
+## Execution
+
+### Step 1: Parse input
+
+The user provides either:
+- A search query: `/mem0:forget auth module decisions`
+- A memory ID: `/mem0:forget <memory_id>`
+
+If no argument, ask: "What should I forget? Provide a search query or memory ID."
+
+### Step 2: Find memories
+
+**If memory ID provided** (looks like a UUID or hex string):
+- Call `get_memory` with the ID to verify it exists.
+- Show: `Found: "<memory content first 120 chars>" (created <date>)`
+
+**If search query provided:**
+- Call `search_memories` with:
+  - `query=<user's query>`
+  - `user_id=<active_user_id>`
+  - `filters={"AND": [{"user_id": "<id>"}, {"app_id": "<project_id>"}]}`
+  - `limit=10`
+- Show numbered list:
+  ```
+  Found <N> memories matching "<query>":
+  1. <content, 120 chars> (type: <type>, created: <date>) [ID: <short_id>]
+  2. ...
+  ```
+
+### Step 3: Confirm
+
+Ask: "Delete which memories? Enter numbers (e.g., 1,3,5), 'all', or 'cancel'."
+
+For a single memory ID, ask: "Delete this memory? [y/N]"
+
+**Never delete without confirmation.** This is destructive.
+
+### Step 4: Delete
+
+For each confirmed memory, call `delete_memory` with the memory ID.
+
+### Step 5: Report
+
+```
+Deleted <N> memories.
+```
+
+If any deletions failed, report which ones and why.