feat(memory): replace MemoryTool to use MempalaceAdapter (config-gated) [phase-5]

[quangdang46]

Problem

jcode's MemoryTool (the LLM-callable tool exposing remember/recall/search/list/forget/tag/link/related actions) currently calls MemoryManager directly. It needs to use MempalaceAdapter when memory_backend = "mempalace" config is set, without changing the tool's external API.

Scope

Files: crates/jcode-app-core/src/tool/memory.rs, crates/jcode-config-types/src/lib.rs

1. Add config option:

   // In AgentsConfig:
   pub memory_backend: MemoryBackend,  // default: MemoryBackend::Native

   pub enum MemoryBackend {
       Native,      // current JSON-based MemoryManager
       Mempalace,   // mempalace MemoryProvider via MempalaceAdapter
   }

2. Backend dispatch in MemoryTool:

   enum MemoryBackend {
       Native(MemoryManager),
       Mempalace(MempalaceAdapter),
   }

   The execute() method dispatches based on which variant is active. Same 8 actions (remember, recall, search, list, forget, tag, link, related) — only the backend changes.

3. Construction: When memory_backend = "mempalace", construct MempalaceAdapter instead of MemoryManager at the tool initialization site in the tool registry.

4. TUI activity events: Wire PalaceBuilder::activity_sink() to emit jcode's MemoryActivity events so the TUI info widget continues working.

5. Feature flag: #[cfg(feature = "mempalace-backend")] gates the mempalace path.

Acceptance Criteria

• memory_backend = "native" (default) works exactly as before
• memory_backend = "mempalace" delegates all 8 tool actions to MempalaceAdapter
• No change to the tool's schema or external behavior
• TUI shows memory activity for both backends
• Config can be set in .jcode/config.json or env var JCODE_MEMORY_BACKEND
• cargo test --workspace passes

Dependencies

• jcode --mode rpc: strict LF-delimited JSONL protocol for IDE / external integrations #12 (MempalaceAdapter must exist)

Reference

jcode MemoryTool: crates/jcode-app-core/src/tool/memory.rs lines 10-428
jcode MemoryInput: lines 45-78
jcode action dispatch: lines 117-428
jcode tool registry: crates/jcode-app-core/src/tool/mod.rs line 245

[quangdang46]

Closed — implemented in PR #364 (merged). MemoryTool dual-backend dispatch (Native/Mempalace) in with feature gate .