9p: add chat.search file for block lookup by ID

Write a block ID to chat.search, read the block content back.
Returns error if block not found.

cmd/olliesrv/internal/agent/chat.go

@@ -7,6 +7,7 @@
 package agent
 
 import (
+	"bytes"
 	"fmt"
 	"sync"
 	"sync/atomic"
@@ -99,6 +100,43 @@ func (ag *Agent) ChatRead(base string) ([]byte, string, error) {
 	return data, fmt.Sprintf("%d", newOffset), nil
 }
 
+// ChatSearchByID returns the block content for the given block ID.
+// Returns the block text (without markers) and true if found, empty and false otherwise.
+func (ag *Agent) ChatSearchByID(blockID string) ([]byte, bool) {
+	if blockID == "" {
+		return nil, false
+	}
+	ag.chatMu.RLock()
+	log := ag.chatLog
+	ag.chatMu.RUnlock()
+
+	// Parse blocks looking for the target ID
+	// Format: [[[role:name#id]]] ... [[[end]]]
+	target := "#" + blockID + "]]]"
+	idx := bytes.Index(log, []byte(target))
+	if idx < 0 {
+		return nil, false
+	}
+
+	// Find the start of this block header
+	headerStart := bytes.LastIndex(log[:idx], []byte("[[["))
+	if headerStart < 0 {
+		return nil, false
+	}
+
+	// Find [[[end]]] after the header
+	endMarker := []byte("[[[end]]]")
+	endIdx := bytes.Index(log[idx:], endMarker)
+	if endIdx < 0 {
+		return nil, false
+	}
+	blockEnd := idx + endIdx + len(endMarker)
+
+	// Extract block including header and end marker
+	block := log[headerStart:blockEnd]
+	return block, true
+}
+
 // --- Plan methods ---
 
 // Plan returns a copy of the plan.

cmd/olliesrv/internal/fs/spec.go

@@ -851,8 +851,19 @@ func buildAgentChildren(a *agent.Agent, s *session.Session) []virtfs.FsNodeDecl
 				return data, nil
 			}),
 			virtfs.Stream(a.ChatRead, a.ChatSignal),
-		),
+			),
-		virtfs.FileNode("state", 0444, // world-readable (non-sensitive)
+			virtfs.FileNode("chat.search", 0660, // rdwr - write blockId, read block
+				virtfs.Doc("Search chat by block ID. Write ID, read block content."),
+				virtfs.Rdwr(func(_ context.Context, data []byte) ([]byte, error) {
+					blockID := strings.TrimSpace(string(data))
+					block, found := a.ChatSearchByID(blockID)
+					if !found {
+						return nil, fmt.Errorf("block not found: %s", blockID)
+					}
+					return block, nil
+				}),
+			),
+			virtfs.FileNode("state", 0444, // world-readable (non-sensitive)
 			virtfs.Doc("Current agent state (idle, calling, thinking, paused)"),
 			virtfs.Read(func() ([]byte, error) {
 				return []byte(a.State() + "\n"), nil