- Remove every box-shadow; panel uses the native sidebar fill surface
(--dsw-specific-sidebar-fill) with a hairline border, the collapse
control becomes the native 36px circular rail button, the active tab
uses the native interactive-bg-active fill, and rows/typography follow
the native 34px/14px session-row recipe.
- New 'Side card' settings section in the DSH Settings shell: open-by-
default for new conversations (boolean) and default width share as a
percent of the window (20-60). New sessions seed from these prefs;
existing per-session layouts stay untouched.
- The settings namespace is read/written through the plugin's own fenced
/sidebar routes calling the settings seam in-process: the DSH settings
RPC domain only serves allowlisted namespaces to configuration clients,
so third-party namespaces cannot use connection.api.settings (reads are
silently filtered, writes refused with 'not exposed'). The seam still
persists to the user settings document with revision-guarded writes.
Menghuan1918