Add file-backed durable memory tools

README.md

@@ -7,10 +7,12 @@ keep the core small, make the seams obvious, and add capability through tools.
 
 - `src/agent.ts` — the agent loop
 - `src/model/openai.ts` — the OpenAI Responses API adapter
+- `src/memory.ts` — file-backed durable memory
 - `src/events.ts` — typed lifecycle events
 - `src/commands.ts` — slash-command registry
 - `src/tools/registry.ts` — tool registration and lookup
 - `src/tools/builtins.ts` — two read-only built-in tools
+- `src/tools/memory.ts` — memory tools backed by markdown files
 - `src/extensions.ts` — project-local extension loader
 - `src/logger.ts` — ordered lifecycle logging
 - `extensions/example.ts` — an example extension that registers `echo`
@@ -108,6 +110,7 @@ The core provides:
 - `/reset` — clear the current conversation history
 - `/save` — persist the current conversation immediately
 - `/logs [on|off]` — toggle lifecycle traces
+- `/memory` — inspect durable memory files
 - `/exit` — leave the interactive session
 
 Extensions can register their own commands.
@@ -123,6 +126,32 @@ You are a helpful agent. Use tools when they are useful, and answer clearly.
 Override it with the `SYSTEM_PROMPT` environment variable. Extensions can also
 append fragments to the final system prompt with `addSystemPrompt(...)`.
 
+## Durable memory
+
+The harness keeps long-lived memory in simple markdown files:
+
+```text
+.harness/memory/
+  MEMORY.md
+  USER.md
+  daily/
+    YYYY-MM-DD.md
+```
+
+The model can choose to use:
+
+- `memory_read` — read `MEMORY.md` or `USER.md`
+- `memory_write` — append durable facts or user preferences
+- `memory_log` — append chronological notes to today's daily file
+
+The split is intentional:
+
+- `MEMORY.md` — durable project or world facts
+- `USER.md` — user preferences and profile
+- `daily/` — episodic notes that are useful as chronology rather than permanent truth
+
+These files are plain markdown so they remain inspectable and easy to edit by hand.
+
 That gives us a clean path to later add:
 
 - more providers