Add ghostty_paste_encode() which encodes paste data for writing to
the terminal pty. It strips unsafe control bytes, wraps in bracketed
paste sequences when requested, and replaces newlines with carriage
returns for unbracketed mode. The input buffer is modified in place
and the encoded result is written to a caller-provided output buffer,
following the same buffer/out_written pattern as the other encode
functions like ghostty_size_report_encode.
Update the c-vt-paste example with an encode_example() demonstrating
the new function and add corresponding @snippet references in the
header documentation.
Extract inline @code blocks from vt headers (size_report.h, modes.h,
sgr.h, paste.h, mouse.h, key.h) into standalone buildable examples
under example/. Each header now uses Doxygen @snippet tags to include
code from the example source files, keeping documentation in sync
with code that is verified to compile and run.
New example projects: c-vt-size-report and c-vt-modes. Existing
examples (c-vt-sgr, c-vt-paste, c-vt-mouse-encode, c-vt-key-encode)
gain snippet markers so their code can be referenced from the headers.
Conceptual snippets in key.h, mouse.h, and key/encoder.h that show
terminal-state usage patterns remain inline since they cannot be
compiled standalone.
