fix(upload): actionable error when file upload hits the extension-relay limit (#13)

DOM.setFileInputFiles is forbidden by Chrome's chrome.debugger API, so upload
always fails over the extension relay with an opaque -32000 "Not allowed". Map
it to a clear message: file upload needs a --launch/direct-CDP session, and
point at the cookies export|set --curl workaround. Note the limit in the core
skill upload line too.

skill-data/core/SKILL.md

@@ -240,7 +240,11 @@ chrome-use pick @e4 --option "Europe"  # ANY combobox (react-select / ARIA /
                                           # (no silent no-op). Use this for custom
                                           # dropdowns where `select` returns ✓ but
                                           # changes nothing.
-chrome-use upload @e5 file1.pdf        # upload file(s)
+chrome-use upload @e5 file1.pdf        # upload file(s) — NOTE: needs a --launch/direct-CDP
+                                          # session. Over the extension relay it CANNOT work
+                                          # (Chrome's chrome.debugger forbids it); chrome-use
+                                          # errors with a hint. Carry your login into a launched
+                                          # session via `cookies export` | `cookies set --curl`.
 chrome-use scroll down 500             # scroll page (up/down/left/right)
 chrome-use scrollintoview @e1          # scroll element into view
 chrome-use drag @e1 @e2                # drag and drop