Add context cancellation to bypass.Submit

bypass.Submit now takes a context and returns early when cancelled.
This allows the stop command to properly cancel pending bypass requests
that haven't been approved or denied yet.

The full context chain is now:
1. stop command -> Interrupt -> cancel actCtx
2. actCtx cancellation -> closes CallTool fid
3. toolsrv proc/new sees closed fid -> propagates ctx cancellation
4. ExecuteTool -> executeBypassDirect -> bypass.Submit
5. bypass.Submit returns ctx.Err() when context is cancelled

cmd/toolsrv/internal/bypass/bypass.go

@@ -4,6 +4,7 @@
 package bypass
 
 import (
+	"context"
 	"crypto/rand"
 	"encoding/hex"
 	"errors"
@@ -29,10 +30,10 @@ var (
 	requests = make(map[string]*Request)
 )
 
-// Submit submits a bypass request and blocks until resolved.
+// Submit submits a bypass request and blocks until resolved or context cancelled.
 // Returns (approved, error). If denied, approved is false and error is nil.
-// If there's an error (e.g., timeout, connection lost), error is non-nil.
-func Submit(cmd, cwd string, env map[string]string) (bool, error) {
+// If context is cancelled, returns (false, ctx.Err()).
+func Submit(ctx context.Context, cmd, cwd string, env map[string]string) (bool, error) {
 	req := &Request{
 		ID:   nextID(),
 		Cmd:  cmd,
@@ -45,8 +46,25 @@ func Submit(cmd, cwd string, env map[string]string) (bool, error) {
 	requests[req.ID] = req
 	mu.Unlock()
 
-	pending <- req
-	<-req.done
+	// Send to pending channel (may block if channel is full)
+	select {
+	case pending <- req:
+	case <-ctx.Done():
+		mu.Lock()
+		delete(requests, req.ID)
+		mu.Unlock()
+		return false, ctx.Err()
+	}
+
+	// Wait for resolution or context cancellation
+	select {
+	case <-req.done:
+	case <-ctx.Done():
+		mu.Lock()
+		delete(requests, req.ID)
+		mu.Unlock()
+		return false, ctx.Err()
+	}
 
 	mu.Lock()
 	delete(requests, req.ID)

cmd/toolsrv/internal/exec/exec.go

@@ -240,7 +240,7 @@ func executeBypassDirect(ctx context.Context, cmd, cwd string, envExtra map[stri
 	}
 
 	// Submit bypass request and wait for approval
-	approved, err := bypass.Submit(cmd, cwd, envMap)
+	approved, err := bypass.Submit(ctx, cmd, cwd, envMap)
 	if err != nil {
 		return "", fmt.Errorf("bypass request failed: %w", err)
 	}