fix(plugin): preserve structure on PreCompact + capture compact summary

Two changes to the compaction flow:

PreCompact: agent stores its summary with infer=False
  on_pre_compact.sh now instructs the agent to call add_memory with
  infer=False. The agent has full conversation context and writes a
  structured summary; without infer=False the platform runs a second
  LLM extraction pass over that summary, losing structure and
  producing fragmented facts. With it, the structured text is
  preserved verbatim. Same guidance added to mem0-mcp/SKILL.md so
  the agent applies it to other already-extracted writes (decisions,
  anti-patterns, conventions).

SessionStart-compact: capture the platform-generated summary
  PreCompact fires BEFORE Claude Code generates its compact summary,
  so the summary is unreachable from that hook. SessionStart-compact
  fires AFTER, so a new background helper (capture_compact_summary.py)
  reads the transcript at that point, finds the isCompactSummary=true
  entry, and stores its content as a separate memory tagged
  metadata.type=compact_summary. The post-compaction bootstrap text
  now tells the agent to layer its recall queries across
  session_state (its own pre-compact summary), compact_summary (the
  platform's condensed view), and topical types like decision /
  anti_pattern.

Net effect: three complementary memory types from one session
boundary, none of which used to be filterable or even captured
correctly.

mem0-plugin/scripts/on_session_start.sh

@@ -65,14 +65,22 @@ Continue where you left off.
 EOF
 
 elif [ "$SOURCE" = "compact" ]; then
+  # Capture the just-generated compact summary in the background.
+  # PreCompact fires too early to see this entry; SessionStart-compact
+  # is the first place isCompactSummary=true is in the transcript.
+  echo "$INPUT" | python3 "$SCRIPT_DIR/capture_compact_summary.py" 2>/dev/null &
+
   cat <<'EOF'
 ## Mem0 Post-Compaction Recovery
 
-Context was just compacted. You may have lost important session context.
+Context was just compacted. The Claude Code-generated compact summary
+is being captured to mem0 in the background as `metadata.type=compact_summary`.
 
-1. Call `search_memories` with queries related to what you were working on to reload relevant knowledge.
-2. Check for any session state memories that were saved before compaction.
-3. Continue working based on the recovered context.
+1. Call `search_memories` to reload context, layering up to three angles:
+   - `metadata.type=session_state` -- the rich pre-compaction summary you wrote
+   - `metadata.type=compact_summary` -- the platform-generated condensed summary just now
+   - `metadata.type=decision` / `anti_pattern` -- specific facts you stored during the session
+2. Continue working from the recovered context.
 EOF
 fi