The 0.8rem (≈11px) tab labels read as undersized chrome against
the 14px panel content and didn't align with the secondary-tier
scale used elsewhere. Bumps:

- font-size 0.8rem → 0.85rem (~12px)
- icon size 0.78rem → 0.82rem to track
- vertical padding 0.25rem → 0.3rem so the slightly larger label
  isn't boxed in
- active tab weight 500 → 600 so the selected state doesn't rely
  on color alone

Affects every consumer of the global SidebarTabs component
(Files, AI, extension sidebar tabs) uniformly.

Threads the new attached-folders list from sendPrompt all the way
to the SDK's additionalDirectories option. Validates each entry
(absolute, exists, not a duplicate of cwd) and drops invalid ones
silently so a typo doesn't blow up the query.

Adds the matching styles: .ai-attach-dropup mirrors the screenshot
dropup, and .ai-context-chip-folder gives the new folder chip an
amber-tinted border and icon so it reads as a distinct kind of
context vs file/selection/live-preview chips.

Plus three new strings for the popup options and folder-picker
title.

Mirrors the Claude Code CLI's default permissions.allow set
(git status / log / diff / show / remote show / branch / ls-files /
rev-parse, plus generic ls / pwd / cat / head / tail / wc / which /
file / stat / echo, and version probes) so the user isn't prompted
for every "look around the repo" command.

Anything containing shell composition characters (; && || | $(...)
backticks < >) still falls through to a user prompt, so chained
destructive operations can't piggy-back on a safe prefix.