docs: add MEMORY_ARCHITECTURE.md — retrieval order, storage layout, data flow

docs/MEMORY_ARCHITECTURE.md

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+# Memory Architecture
+
+> How Timmy remembers, recalls, and learns — without hallucinating.
+
+Refs: Epic #367 | Sub-issues #368, #369, #370, #371, #372
+
+## Overview
+
+Timmy's memory system uses a **Memory Palace** architecture — a structured, file-backed knowledge store organized into rooms and drawers. When faced with a recall question, the agent checks its palace *before* generating from scratch.
+
+This document defines the retrieval order, storage layers, and data flow that make this work.
+
+## Retrieval Order (L0–L5)
+
+When the agent receives a prompt that looks like a recall question ("what did we do?", "what's the status of X?"), the retrieval enforcer intercepts it and walks through layers in order:
+
+| Layer | Source | Question Answered | Short-circuits? |
+|-------|--------|-------------------|------------------|
+| L0 | `identity.txt` | Who am I? What are my mandates? | No (always loaded) |
+| L1 | Palace rooms/drawers | What do I know about this topic? | Yes, if hit |
+| L2 | Session scratchpad | What have I learned this session? | Yes, if hit |
+| L3 | Artifact retrieval (Gitea API) | Can I fetch the actual issue/file/log? | Yes, if hit |
+| L4 | Procedures/playbooks | Is there a documented way to do this? | Yes, if hit |
+| L5 | Free generation | (Only when L0–L4 are exhausted) | N/A |
+
+**Key principle:** The agent never reaches L5 (free generation) if any prior layer has relevant data. This eliminates hallucination for recall-style queries.
+
+## Storage Layout
+
+```
+~/.mempalace/
+  identity.txt              # L0: Who I am, mandates, personality
+  rooms/
+    projects/
+      timmy-config.md        # What I know about timmy-config
+      hermes-agent.md        # What I know about hermes-agent
+    people/
+      alexander.md           # Working relationship context
+    architecture/
+      fleet.md               # Fleet system knowledge
+      mempalace.md           # Self-knowledge about this system
+  config/
+    mempalace.yaml           # Palace configuration
+
+~/.hermes/
+  scratchpad/
+    {session_id}.json        # L2: Ephemeral session context
+```
+
+## Components
+
+### 1. Memory Palace Skill (`mempalace.py`) — #368
+
+Core data structures:
+- `PalaceRoom`: A named collection of drawers (topics)
+- `Mempalace`: The top-level palace with room management
+- Factory constructors: `for_issue_analysis()`, `for_health_check()`, `for_code_review()`
+
+### 2. Retrieval Enforcer (`retrieval_enforcer.py`) — #369
+
+Middleware that intercepts recall-style prompts:
+1. Detects recall patterns ("what did", "status of", "last time we")
+2. Walks L0→L4 in order, short-circuiting on first hit
+3. Only allows free generation (L5) when all layers return empty
+4. Produces an honest fallback: "I don't have this in my memory palace."
+
+### 3. Session Scratchpad (`scratchpad.py`) — #370
+
+Ephemeral, session-scoped working memory:
+- Write-append only during a session
+- Entries have TTL (default: 1 hour)
+- Queried at L2 in retrieval chain
+- Never auto-promoted to palace
+
+### 4. Memory Promotion — #371
+
+Explicit promotion from scratchpad to palace:
+- Agent must call `promote_to_palace()` with a reason
+- Dedup check against target drawer
+- Summary required (raw tool output never stored)
+- Conflict detection when new memory contradicts existing
+
+### 5. Wake-Up Protocol (`wakeup.py`) — #372
+
+Boot sequence for new sessions:
+```
+Session Start
+  │
+  ├─ L0: Load identity.txt
+  ├─ L1: Scan palace rooms for active context
+  ├─ L1.5: Surface promoted memories from last session
+  ├─ L2: Load surviving scratchpad entries
+  │
+  └─ Ready: agent knows who it is, what it was doing, what it learned
+```
+
+## Data Flow
+
+```
+              ┌──────────────────┐
+              │  User Prompt     │
+              └────────┬─────────┘
+                       │
+              ┌────────┴─────────┐
+              │ Recall Detector  │
+              └────┬───────┬─────┘
+                   │           │
+            [recall]     [not recall]
+                   │           │
+          ┌───────┴────┐    ┌──┬─┴───────┐
+          │ Retrieval  │    │ Normal Flow │
+          │ Enforcer   │    └─────────────┘
+          │ L0→L1→L2  │
+          │ →L3→L4→L5│
+          └──────┬─────┘
+                 │
+          ┌──────┴─────┐
+          │  Response    │
+          │ (grounded)  │
+          └────────────┘
+```
+
+## Anti-Patterns
+
+| Don't | Do Instead |
+|-------|------------|
+| Generate from vibes when palace has data | Check palace first (L1) |
+| Auto-promote everything to palace | Require explicit `promote_to_palace()` with reason |
+| Store raw API responses as memories | Summarize before storing |
+| Hallucinate when palace is empty | Say "I don't have this in my memory palace" |
+| Dump entire palace on wake-up | Selective loading based on session context |
+
+## Status
+
+| Component | Issue | PR | Status |
+|-----------|-------|----|--------|
+| Skill port | #368 | #374 | In Review |
+| Retrieval enforcer | #369 | #374 | In Review |
+| Session scratchpad | #370 | #374 | In Review |
+| Memory promotion | #371 | — | Open |
+| Wake-up protocol | #372 | #374 | In Review |