perf: make ClearScreen O(h) instead of O(h×w) canvas ops

ClearScreen was calling eraseRegion which iterated every cell, each
doing expensive Canvas.Paint linked-list manipulation. Now full rows
are cleared via clearRow which resets the canvas row to a single
Region in O(1), reducing canvas work from O(h×w) to O(h). Partial
rows at the cursor still use eraseRegion.

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

fix panic when growing height + shrinking width

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

preserve Format.Render compatibility

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

set initial fg/bg

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

reduce Format memory footprint

sacrifice overline and cross-out so we can squeeze it all in a uint8

when viewing 19336 lines of output this saves about 100MB of RAM:

https://dagger.cloud/dagger/traces/c3fa969a260b94dc6a85dfe313885537

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

better alt/main-screen state handling

support resizing only x or y

maybe i should tag less often

render with lock

new auto-resize semantics + constructor

initial midterm release

Starting over at v0.1.0 to reflect the new name, since older tags would
point to a different Go module entirely.

Based on the vt100 package, but expanded to support vt102 features and
anything else I notice missing while using it for interactive shells and
TUI applications.