v1.20.0

Second of the two PRs that replace #91 (docs/DESIGN-attachments.md holds the model this code keeps).

Added

• ask takes attachments: up to 8 image or PDF files (png, jpg, jpeg, webp, pdf; 10 MB each, 14 MB together —
  this server's cap, under every figure Google publishes; base64 adds a third), sent as inlineData parts before the
  question in the user turn, with or without a Context Cache (a cache hit without attachments still sends the bare
  prompt). They belong to one question, never to the workspace cache. A path must be inside the workspace (the same
  realpath jail as ask_agentic, its secret rules included), a symlink is refused, every file is checked (type, size,
  readability) by stat before any is read, read through an O_NOFOLLOW descriptor whose device and inode must be the
  ones recorded at inspection (a file swapped, replaced, deleted or grown in between is refused), and its first bytes
  must match the declared type. Their tokens are what Gemini counts: one free countTokens call on the parts, whose
  total enters the size preflight, the budget reservation and the TPM throttle (measured 2026-10-01: a 1×1 PNG is
  1090 tokens on gemini-3-flash and 259 on 2.5-flash-lite, so no local figure would do); a count that cannot be
  obtained refuses the call (ATTACHMENT_TOKENS_UNCOUNTED, retryable). Inspection, read and count happen before the
  preflight and every reservation, so a bad file costs nothing: a model without vision is ATTACHMENTS_UNSUPPORTED,
  a bad file ATTACHMENT_INVALID (retryable: false), a request whose conservative size (the attachments encoded, the
  workspace bodies with their markers, the prompt, the system instruction, the JSON framing) would cross Google's
  20 MB inline limit REQUEST_TOO_LARGE, the ask_agentic fallback cannot carry them
  and says so.
  structuredContent.attachments lists what was sent and attachmentTokens what Gemini counted. The latest-vision
  alias finally has an input to see.

Changed

• The Flash-Lite models count as vision-capable (Google lists image and PDF input on them; countTokens on
  gemini-2.5-flash-lite counted an inline PNG and PDF on 2026-10-01), so attachments work on a Flash-Lite model
  named explicitly or through latest-lite (latest-vision keeps resolving among the reasoning and fast tiers).