docs: update ROADMAP for today's fixes and two stale entries
Corrected the terminfo entry's now-false claim that bce isn't
implemented (it has been since an unrelated later commit that had no
reason to revisit this file) and folded in what that caused plus the
cr/bel/rep/tbc audit findings as a "Since then" continuation, matching
this file's existing pattern for amending completed entries rather
than leaving the original claim to contradict reality.
Also documented, in the same style, on their existing entries:
REPLY_BUF_MAX (64-byte reply buffer truncation), the bare-LF column
reset fix, and XTGETTCAP replies -- all real fixes from this session
that had no roadmap trace, plus the new PTY_DEBUG_LOG_BUILD tooling
flag under Test infrastructure.
Found two items unrelated to today's work already stale: the
whole-grid-to-[]string snapshot helper (Testing improvements) has
existed since an earlier commit (grid_to_lines) but was still listed
as not-yet-done -- marked [x]. Left the CSI-param boundary-value table
item alone: real per-boundary test coverage exists, but not as the
literal table-driven structure that item specifically asks for.