feat: Discard all, claude-style image pastes, large local drops, per-account / list

- Changes panel: **Discard all** beside Commit discards every non-conflicted
  file in one `discard`, after a dialog naming how many untracked files go.
- Terminal: a `claude` pane gets dropped/pasted images as bare paths (shown as
  `[Image #n]`) and other files as `@` mentions (`claudePastes`); a local
  browser's copied `file://` paths and text-drag file lists paste by path.
- `POST /api/run/drop-file`: a loopback browser outside server mode may drop
  up to 2 GB, streamed to disk; remote stays 20 MB.
- cc-config skills/commands/plugins read the USER scope of the account the
  pane runs as (S3 member home by `cwd`), never another user's or the host's
  for a non-admin without an account; the run form passes its cwd to plugins.

client/src/components/run/RunSetup.tsx

@@ -308,7 +308,7 @@ export function PromptEditor({
     Promise.all([
       api.ccConfig.commands(undefined, fileCwd).catch(() => ({ items: [] as CcMdItem[] })),
       api.ccConfig.skills(undefined, fileCwd).catch(() => ({ items: [] as CcMdItem[] })),
-      api.ccConfig.plugins().catch(() => ({ plugins: [] })),
+      api.ccConfig.plugins(fileCwd).catch(() => ({ plugins: [] })),
     ]).then(([c, sk, pl]) => {
       // A plugin's commands and skills are addressed as `/<plugin>:<name>`; one
       // installed at both user and project scope is listed once.