fix(clipboard): dashboard Ctrl+C direct copy; TUI honest feedback; HERMES_TUI_FORCE_OSC52

- Dashboard copy: direct Clipboard API on Ctrl+C/Cmd+C (user gesture);
  send Escape to TUI to clear selection; Ctrl+Shift+C kept as fallback.
- TUI /copy: copySelection() async; only reports success if OSC52 emitted.
- Add HERMES_TUI_FORCE_OSC52 env var to override native-tool detection.
- Fixes "copied N chars" false-positive when clipboard backend absent.

Changes:
  web/src/pages/ChatPage.tsx — direct navigator.clipboard.writeText
  ui-tui/packages/hermes-ink/src/ink/ink.tsx — async copySelection
  ui-tui/packages/hermes-ink/src/ink/termio/osc.ts — HERMES_TUI_FORCE_OSC52
  ui-tui/src/app/slash/commands/core.ts — async /copy with honest feedback

ui-tui/packages/hermes-ink/src/ink/ink.tsx

@@ -1301,7 +1301,13 @@ export default class Ink {
    * highlight. Matches iTerm2's copy-on-select behavior where the selected
    * region stays visible after the automatic copy.
    */
-  copySelectionNoClear(): string {
+  /**
+   * Copy the current text selection to the system clipboard without clearing the
+   * selection. Returns the copied text on success (empty if no selection or
+   * clipboard operation failed). Success is determined by whether an OSC 52
+   * sequence was emitted (native/tmux paths do not produce a sequence).
+   */
+  async copySelectionNoClear(): Promise<string> {
     if (!hasSelection(this.selection)) {
       return ''
     }
@@ -1309,28 +1315,36 @@ export default class Ink {
     const text = getSelectedText(this.selection, this.frontFrame.screen)
 
     if (text) {
-      void setClipboard(text).then(raw => {
+      try {
+        const raw = await setClipboard(text)
         if (raw) {
           this.options.stdout.write(raw)
-        } else if (process.env.HERMES_TUI_DEBUG_CLIPBOARD) {
+          return text
+        }
+        if (process.env.HERMES_TUI_DEBUG_CLIPBOARD) {
           console.error('[clipboard] [osc52] no sequence emitted — native clipboard or tmux buffer path in use')
         }
-      })
+      } catch (err) {
+        if (process.env.HERMES_TUI_DEBUG_CLIPBOARD) {
+          console.error('[clipboard] [osc52] error:', err)
+        }
+      }
     }
 
-    return text
+    return ''
   }
 
   /**
    * Copy the current text selection to the system clipboard via OSC 52
-   * and clear the selection. Returns the copied text (empty if no selection).
+   * and clear the selection. Returns the copied text (empty if no selection
+   * or clipboard operation failed).
    */
-  copySelection(): string {
+  async copySelection(): Promise<string> {
     if (!hasSelection(this.selection)) {
       return ''
     }
 
-    const text = this.copySelectionNoClear()
+    const text = await this.copySelectionNoClear()
     clearSelection(this.selection)
     this.notifySelectionChange()
 

ui-tui/packages/hermes-ink/src/ink/termio/osc.ts

@@ -84,7 +84,11 @@ export function getClipboardPath(): ClipboardPath {
 }
 
 export function shouldEmitClipboardSequence(env: NodeJS.ProcessEnv = process.env): boolean {
-  const override = (env.HERMES_TUI_CLIPBOARD_OSC52 ?? env.HERMES_TUI_COPY_OSC52 ?? '').trim()
+  const override = (
+    env.HERMES_TUI_FORCE_OSC52 ??
+    env.HERMES_TUI_CLIPBOARD_OSC52 ??
+    env.HERMES_TUI_COPY_OSC52 ?? ''
+  ).trim()
 
   if (ENV_ON_RE.test(override)) {
     return true