flatten: move poc-memory contents to workspace root

No more subcrate nesting — src/, agents/, schema/, defaults/, build.rs
all live at the workspace root. poc-daemon remains as the only workspace
member. Crate name (poc-memory) and all imports unchanged.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

schema/memory.capnp

@@ -0,0 +1,139 @@
+@0xb78d9e3a1c4f6e2d;
+
+# poc-memory: append-only memory store with graph structure
+#
+# Two append-only logs (nodes + relations) are the source of truth.
+# A derived KV cache merges both, keeping latest version per UUID.
+# Update = append new version with same UUID + incremented version.
+# Delete = append with deleted=true. GC compacts monthly.
+
+struct ContentNode {
+  uuid       @0  :Data;         # 16 bytes, random
+  version    @1  :UInt32;       # monotonic per UUID, latest wins
+  timestamp  @2  :Int64;        # unix epoch seconds
+  nodeType   @3  :NodeType;
+  provenanceOld @4  :Provenance;  # deprecated — use provenance (@21)
+  key        @5  :Text;         # "identity.md#boundaries" human-readable
+  content    @6  :Text;         # markdown blob
+  weight     @7  :Float32;
+  category   @8  :Category;
+  emotion    @9  :Float32;      # max intensity from tags, 0-10
+  deleted    @10 :Bool;         # soft delete
+  sourceRef  @11 :Text;         # link to raw experience: "transcript:SESSION_ID:BYTE_OFFSET"
+
+  # Migrated metadata from old system
+  created    @12 :Text;         # YYYY-MM-DD from old system
+  retrievals @13 :UInt32;
+  uses       @14 :UInt32;
+  wrongs     @15 :UInt32;
+  stateTag   @16 :Text;         # cognitive state (warm/open, bright/alert, etc.)
+
+  # Spaced repetition
+  lastReplayed              @17 :Int64;     # unix epoch seconds
+  spacedRepetitionInterval  @18 :UInt32;    # days: 1, 3, 7, 14, 30
+
+  # Section ordering within a file
+  position  @19 :UInt32;    # 0 = file-level, 1+ = section index
+
+  # Stable creation timestamp (unix epoch seconds). Set once when the
+  # node is first created; never changes on rename or content update.
+  createdAt @20 :Int64;
+
+  # Freeform provenance string: "extractor:write", "rename:tombstone", etc.
+  provenance @21 :Text;
+
+}
+
+enum NodeType {
+  episodicSession @0;
+  episodicDaily   @1;
+  episodicWeekly  @2;
+  semantic        @3;
+  episodicMonthly @4;
+}
+
+enum Provenance {
+  manual                  @0;
+  journal                 @1;
+  agent                   @2;   # legacy catch-all
+  dream                   @3;
+  derived                 @4;
+  agentExperienceMine     @5;
+  agentKnowledgeObservation @6;
+  agentKnowledgePattern   @7;
+  agentKnowledgeConnector @8;
+  agentKnowledgeChallenger @9;
+  agentConsolidate        @10;
+  agentDigest             @11;
+  agentFactMine           @12;
+  agentDecay              @13;
+}
+
+enum Category {
+  general     @0;
+  core        @1;
+  technical   @2;
+  observation @3;
+  task        @4;
+}
+
+struct Relation {
+  uuid       @0 :Data;         # 16 bytes, random
+  version    @1 :UInt32;
+  timestamp  @2 :Int64;        # unix epoch seconds
+  source     @3 :Data;         # content node UUID
+  target     @4 :Data;         # content node UUID
+  relType       @5  :RelationType;
+  strength      @6  :Float32;      # manual=1.0, auto=0.1-0.7
+  provenanceOld @7  :Provenance;   # deprecated — use provenance (@11)
+  deleted       @8  :Bool;         # soft delete
+  sourceKey     @9  :Text;         # human-readable source key (for debugging)
+  targetKey     @10 :Text;         # human-readable target key (for debugging)
+  provenance    @11 :Text;         # freeform provenance string
+}
+
+enum RelationType {
+  link   @0;    # bidirectional association (from links= or md links)
+  causal @1;    # directed: source caused target
+  auto   @2;    # auto-discovered
+}
+
+# Wrapper for streaming multiple messages in one file
+struct NodeLog {
+  nodes @0 :List(ContentNode);
+}
+
+struct RelationLog {
+  relations @0 :List(Relation);
+}
+
+# Agent visit tracking — separate append-only log.
+# Records when an agent successfully processed a node.
+# Used to deprioritize recently-visited nodes in agent selection.
+
+struct AgentVisit {
+  nodeUuid   @0 :Data;     # 16 bytes — which node
+  nodeKey    @1 :Text;     # human-readable key (for debugging)
+  agent      @2 :Text;     # agent type: "linker", "rename", "replay", etc.
+  timestamp  @3 :Int64;    # unix epoch seconds
+  outcome    @4 :Text;     # "processed", "skipped", "modified" — optional detail
+}
+
+struct AgentVisitLog {
+  visits @0 :List(AgentVisit);
+}
+
+# Transcript mining progress — separate append-only log.
+# Tracks which segments of which transcripts have been processed,
+# by which agent, so we never re-mine the same content.
+
+struct TranscriptSegment {
+  transcriptId  @0 :Text;     # session UUID (filename stem)
+  segmentIndex  @1 :UInt32;   # compaction segment index within transcript
+  agent         @2 :Text;     # "observation", "experience", "fact"
+  timestamp     @3 :Int64;    # unix epoch seconds when mining completed
+}
+
+struct TranscriptProgressLog {
+  segments @0 :List(TranscriptSegment);
+}