Bug Description

When multiple agents (sonnet, opus, haiku) share the same workspace, ensureCollections() fails to create agent-scoped collections (e.g., memory-root-opus) because another agent's collection (e.g., memory-root-sonnet) already occupies the same path + pattern slot in the qmd database.

Root Cause

In qmd-manager, ensureCollections() calls addCollection() which runs:

qmd collection add <path> --name memory-root-opus --mask MEMORY.md

qmd CLI rejects this with:

A collection already exists for this path and pattern:
  Name: memory-root-sonnet (qmd://memory-root-sonnet/)
  Pattern: MEMORY.md

The error handler isCollectionAlreadyExistsError() checks for "already exists" in the message and returns true, causing the code to continue — treating it as if memory-root-opus was successfully created. But it was not.

Impact

• Agent-scoped memory collections are never created for agents that start after the first one
• memory_search fails with "Collection not found" for those agents
• openclaw status reports "vector ready" while semantic search is completely broken

Suggested Fix

isCollectionAlreadyExistsError() should distinguish between:

1. Same name exists (truly OK to skip) — check if message contains the exact collection name being created
2. Same path+pattern exists under a different name (NOT OK) — should remove the conflicting collection first, then retry

Environment

• OpenClaw 2026.2.21-2, macOS, 3 agents (sonnet/opus/haiku)
• qmd with per-agent XDG_CONFIG_HOME/XDG_CACHE_HOME isolation
• Each agent gets its own SQLite DB at ~/.openclaw/agents/{agentId}/qmd/xdg-cache/qmd/index.sqlite