opencode native 0.10.0

Added

• src/bench_test.odin: the program on its heavy cases in the test's process, no server (a conversation of 150 answers,
  400 sessions); -define:OCC_BENCH=true times them. docs/performance.md: what was measured.

Changed

• Built with Odin dev-2026-11 (odin.version, the CI's archives pinned by SHA-256, flake.nix): core:image's pixels are
  a [dynamic]u8.
• gui_toolkit 0.70.0: menus are denser and scroll when taller than the window; threads shaping text share the word cache's lock.
• The sidebar builds the sessions it shows (a lazy column, as the conversation): with 400 sessions a frame took 8.4 ms,
  now 1.6 ms; typing, scrolling and a streamed answer 10 to 11 ms, now 2.4 to 2.5 ms (docs/performance.md).
• A faster start: the graphics device is made while the rest starts, the fonts load meanwhile (first frame 200 -> 183 ms).
  --frames=N says how long the first frame took.

Windows 10 and 11 (x64): one executable; run it, or install it for your user from its Setup (title bar menu > Setup...).
Linux (x64): the archive holds one program; run it, or ./opencode-native --install (an entry in the applications menu). Needs Vulkan, libxkbcommon, fontconfig, Wayland or X11.

It finds the opencode server of the computer by itself (another one: --url, or the status bar's server menu).