Add uname, /uname and scp (key or masked password) in the Shell

- uname in the console and /uname in IRC: the firmware, its version and the chip
- scp: one file between the card and a trusted server, over SSH, with the
  device's key or a password asked (masked) in the Shell
- shared libssh helpers in src/platform/libssh_util
- README, user guide, command reference and a how-to updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

src/apps/shell_app.cpp

@@ -33,6 +33,9 @@ void ShellApp::onEnter() {
 
 // Nothing is kept once it's left: the ring, the lines and the list of commands all go (Q207).
 void ShellApp::onExit() {
+    if (password_ && abort) abort();
+    password_ = false;
+    input_.setText("");
     console.closeShellRing();
     console.shellShowsAll(false);
     open_ = false;
@@ -49,6 +52,11 @@ void ShellApp::update(uint32_t) {
         if (skipped) log_.add("[... " + std::to_string(skipped) + " bytes lost: more was printed than fits]");
         log_.feed(reinterpret_cast<const char*>(buf), n);
     }
+    if (!password_ && asking && asking()) {  // after the question has been printed above
+        password_ = true;
+        input_.setText("");
+        requestRedraw();
+    }
     if (log_.revision() != seenRevision_) {
         seenRevision_ = log_.revision();
         requestRedraw();
@@ -114,6 +122,23 @@ bool ShellApp::onKey(const KeyEvent& e) {
         log_.add(console.shellShowsAll() ? "Showing everything the console prints." : "Showing only the replies to your commands.");
         return true;
     }
+    if (password_) {  // masked, kept nowhere: not in the history, not in the log
+        switch (e.key) {
+            case Key::Char: input_.insert(e.ch); break;
+            case Key::Delete: input_.backspace(); break;
+            case Key::Select: {
+                std::string typed = input_.text();
+                input_.setText("");
+                password_ = false;
+                log_.add("> " + std::string(typed.size(), '*'));
+                if (answer) answer(typed);
+                typed.assign(typed.size(), '\0');
+                break;
+            }
+            default: return false;  // Back leaves the Shell, which cancels the copy
+        }
+        return true;
+    }
     std::string recalled;
     switch (e.key) {
         case Key::Char: input_.insert(e.ch); break;
@@ -197,7 +222,13 @@ void ShellApp::draw(Canvas& c) {
     }
     c.setTextDatum(top_left);
 
-    widgets::lineEditor(c, input_, {2, area.y + area.h - inputH, area.w - 4, 0});
+    if (password_) {
+        LineEditor stars(240);
+        stars.setText(std::string(input_.text().size(), '*'));
+        widgets::lineEditor(c, stars, {2, area.y + area.h - inputH, area.w - 4, 0});
+    } else {
+        widgets::lineEditor(c, input_, {2, area.y + area.h - inputH, area.w - 4, 0});
+    }
     if (confirm_) widgets::dialog(c, "Delete?", question_, *confirm_);
 }
 

src/apps/shell_app.h

@@ -36,6 +36,12 @@ class ShellApp : public App {
     ShellApp(Run run, Probe probe, List list, Count count, const char* helpText, AppManager& apps)
         : run_(std::move(run)), probe_(std::move(probe)), list_(std::move(list)), count_(std::move(count)), helpText_(helpText), apps_(apps) {}
 
+    // `scp` asking for a password: while asking() is true, the next line typed is masked and goes to
+    // answer() instead of the console; leaving the Shell calls abort().
+    std::function<bool()> asking;
+    std::function<void(const std::string&)> answer;
+    std::function<void()> abort;
+
     void onEnter() override;
     void onExit() override;
     bool onKey(const KeyEvent& e) override;
@@ -63,6 +69,7 @@ class ShellApp : public App {
     uint32_t ringPos_ = 0, seenRevision_ = 0;
     int scroll_ = 0;  // wrapped lines scrolled back from the bottom
     bool open_ = false;
+    bool password_ = false;  // the line being typed is a password
 };
 
 }  // namespace roro