v0.7.1: Streaming + Markdown + URLs + Interrupt — TDD

Stream-chunk protocol: SSE streaming via provider-openai-stream,
cascade-stream with fboundp guard in think(). TUI renders live.

Stream interrupt: Esc during streaming marks [interrupted], finalizes msg.
SSE cancel infrastructure: *stream-cancel* check in read loop.

Markdown inline: **bold**, *italic*, `code` via parse-markdown-spans.
Code blocks: parse-markdown-blocks + syntax-highlight (keywords/strings/fns).
URL detection + Tab-to-activate: https:// URLs in dim, Tab opens.

Watchdog: 30s stall detection via Dexador read-timeout.
[streaming] indicator in status bar.

Pre-existing TUI test fixes (7): first→aref, nil→zerop, add-msg arg.

Core: 65/65  Neuro: 13/13  TUI View: 22/22  TUI Main: 65/65
Total: 165 tests, 0 failures.

lisp/core-reason.lisp

@@ -76,6 +76,7 @@
   (let* ((sensor (proto-get (proto-get context :payload) :sensor))
          (active-skill (find-triggered-skill context))
          (tool-belt (generate-tool-belt-prompt))
+          (reply-stream (proto-get context :reply-stream)) ; v0.7.1: streaming
           (global-context (if (fboundp 'context-assemble-cached)
                               (context-assemble-cached context sensor)
                               (if (fboundp 'context-assemble-global-awareness)
@@ -128,9 +129,20 @@
                                          (concatenate 'string (string #\Newline) standing-mandates-text)
                                          "")
                                      tool-belt (or global-context "") system-logs))))
-    (let* ((thought (backend-cascade-call raw-prompt
-                                          :system-prompt system-prompt
-                                          :context context))
+    (let* ((thought (if (and reply-stream (fboundp 'cascade-stream))  ; v0.7.1: streaming
+                       (let ((acc (make-string-output-stream)))
+                         (funcall 'cascade-stream raw-prompt system-prompt
+                                  (lambda (delta)
+                                    (when reply-stream
+                                      (format reply-stream "~a"
+                                              (frame-message (list :type :stream-chunk
+                                                                   :payload (list :text delta))))
+                                      (finish-output reply-stream))
+                                    (write-string delta acc)))
+                         (get-output-stream-string acc))
+                       (backend-cascade-call raw-prompt
+                                             :system-prompt system-prompt
+                                             :context context)))
            (tool-calls (and (listp thought) (getf thought :tool-calls))))
       ;; v0.5.0: cost tracking after successful cascade
       (when (and (fboundp 'cost-track-backend-call)