v0.8.5: WebUI process timeline, Gemini-style images, aligned layout

Process timeline: a run of consecutive thinking and tool calls is one
block that folds to a single line ("思考 4 次 · 工具 6 次"; while running
it shows the current action) and opens into a compact timeline, one row
per thought or call. Visible text, a note or the next prompt closes the
block; history and the live stream follow the same rule. show_thinking
now also applies while streaming instead of forcing thoughts open.

Layout: the avatar gutter and the flex-wrap that dropped it under long
answers are gone, so answer, process blocks, notes and composer share one
left edge. The text column and composer are both 720px (--content); the
rail and run panel grow with clamp() on wide screens. A rebuild after
each turn no longer replays every entrance animation, and the turn time
survives it. Message actions are icon buttons and only appear under text.

Images: a prompt's images sit above the bubble, right-aligned (one keeps
its shape, several are 152px rounded tiles) and open in a lightbox (Esc,
arrow keys). Images uploaded from the page show as thumbnails over the
composer and appear on the prompt as soon as it is sent.

Also: ?theme= is no longer overridden by app.js, the user bubble is
visible in the light theme, and the narrow top bar no longer wraps.

include/cst_version.h

@@ -3,7 +3,7 @@
 
 #define CST_VERSION_MAJOR 0
 #define CST_VERSION_MINOR 8
-#define CST_VERSION_PATCH 4
+#define CST_VERSION_PATCH 5
 
 #define CST_VERSION_STR_(x) #x
 #define CST_VERSION_STR(x) CST_VERSION_STR_(x)