* fix(terminal): keep WebGL glyph atlas pages within the shader sampler budget
The fragment shader has sampler slots for maxAtlasPages (16 on most Macs)
and leaves outColor uninitialized for any higher page index, so glyphs
rasterized onto pages past the budget render as garbled pixels. Long
sessions grow past the budget via the merge fallback, and the previous
wipe fix re-activated those unbindable pages, so every atlas wipe
re-allocated glyphs onto them (post-wipe allocation prefers the last,
highest-index active page) and garbled whole panes mid-stream.
Fix, matching the direction xterm.js maintainers are pursuing upstream
(xtermjs/xterm.js#6043): a shared _evictAllPages resets the atlas to one
fresh page, called from clearTexture and from the two allocation paths
that could otherwise push a page past the budget (merge fallback and
oversized-glyph page creation), so the page count can never exceed the
renderer's texture capacity. Defensive backstops: a one-time warn plus
bind-loop clamp, and an else branch in the generated shader so an
unexpected overflow renders blank instead of undefined pixels.
* test(terminal): cover WebGL atlas sampler budget
* fix(terminal): align WebGL atlas invalidation source
59a7fffcd6