feat(terminal,cli): docker_extra_args + display.timestamps

Two independent opt-in QoL toggles, both off by default.

terminal.docker_extra_args:
- List of extra flags appended verbatim to docker run after security
  defaults. Useful for adding capabilities (e.g. --cap-add SETUID) or
  other docker run options not exposed by existing config keys.
- Non-string entries are logged and skipped.
- Also available via TERMINAL_DOCKER_EXTRA_ARGS='[...]' env var.

display.timestamps:
- Appends [HH:MM] to user input bullet and the assistant response box
  header. Single hub in _format_submitted_user_message_preview()
  covers both single-line and multi-line user previews; assistant
  response label gets the timestamp at box-open time.

Closes #1569 (timestamps).

Co-authored-by: Mibayy <Mibayy@users.noreply.github.com>

cli-config.yaml.example

@@ -203,6 +203,12 @@ terminal:
 #   docker_forward_env:
 #     - "GITHUB_TOKEN"
 #     - "NPM_TOKEN"
+#   # Optional: extra flags passed verbatim to docker run (appended after security defaults).
+#   # Useful for adding capabilities (e.g. apt installs needing SETUID) or custom options.
+#   # Example: add a Linux capability not included by default
+#   # docker_extra_args:
+#   #   - "--cap-add"
+#   #   - "SETUID"
 
 # -----------------------------------------------------------------------------
 # OPTION 4: Singularity/Apptainer container
@@ -947,6 +953,9 @@ display:
   #   false: Wait for the full response before rendering
   streaming: true
 
+  # Show [HH:MM] timestamps on user input and assistant response labels.
+  # timestamps: false
+
   # ───────────────────────────────────────────────────────────────────────────
   # Skin / Theme
   # ───────────────────────────────────────────────────────────────────────────