TUI keys: register both CSI and SS3 forms of the cursor/Home/End keys and
the xterm modifier sequences when terminfo lacks them, so an arrow sent in
the "other" form no longer turns into Esc + a typed letter. Up/Down move by
visual (soft-wrapped) row, and the draft survives a trip through history.
scripts/tui_keys drives the TUI in a pty to check all of this.
Images: text inside a multimodal content array is now a {"type":"text"}
part; DeepSeek rejected the bare string with HTTP 422. deepseek-flash
(and its deepseek-chat / deepseek-reasoner aliases) read images, so the
registry marks them vision; deepseek-v4-pro stays text only.
CI: models.c lost _DEFAULT_SOURCE in 0.7.0 and gmtime_r broke the musl
build; tests sleep with poll() instead of usleep for the same reason.
