Comment flush edge cases: EOF trailing comment moves to its own line; pad-space artifacts break print idempotency

Three boundary conditions in the comment flush machinery (all with parser-native locs):

1. A trailing comment at EOF without a final newline moves onto its own line:

   console.log(1); // keep me
   

   (no trailing \n) prints

   console.log(1);
   // keep me
   

   Line-bound directives (eslint-disable-line and friends) stop covering their statement. Root: flush_trailing_comments requires before(comment.loc.end, next) STRICTLY, and at EOF-no-newline the comment ends exactly at Program.loc.end.

2. Multiline block comment before a statement leaves a stray pad space (the newline after */ is intentional per #82 - the leftover is the pad):

   /* lead
    */ console.log(1);
   

   prints */\n console.log(1); - note the leading space. The next print of that output drops it, so the first print is not a fixed point.

3. Comment-only file without a final newline grows a space per print:

   // alone
   

   (no trailing \n) prints // alone - the pad space intended for a following statement lands INSIDE the line-comment token, so every reprint grows the comment's text by one space (non-converging).

Context: found by a parse -> print -> reparse structural gate over a ~8.5k-file TS/JS corpus while adopting esrap in core-js's build plugin, then re-verified in isolation. esrap 2.3.5; the ASTs below come from @typescript-eslint/typescript-estree 8.67 with loc/range enabled, so the repros are independent of our own (oxc-based) pipeline.

Start at the flush_trailing_comments machinery and reproduce the three snippets described in the issue, including the EOF and multiline-comment boundaries. Verify that trailing comments stay on the intended line, block-comment padding is not emitted, and comment-only files print to the same text on repeated runs.