v0.4.2

The documentation set, brought up to what 0.4 actually does.

Two statements were wrong and the rest understated the crate by a
release or two. No library code changed.

0.4.1 was tagged for exactly this content and never published: its
release run caught a latent race in this suite's own UTF-8 mouse test —
padding written after a click could be read by the script's exit guard
instead of by head, ending the child early so the next write failed
with EIO. Fixed before publishing, so the version on crates.io is the one
whose gates all passed.

Fixed

• The README no longer contradicts itself about scrollback. Its
  limitations section was still headed (v0.3) and still opened with "No
  scrollback assertions" — sixty lines below the paragraph explaining that
  scrollback is retained, 1000 rows by default. Since the README is the
  crates.io front page, the first thing a reader learned about 0.4's
  headline feature was that it did not exist. The section now states the
  bounds that actually hold: history is capped, text only and unreflowed;
  wait_frame needs the application to opt into DEC 2026 and retains eight
  frames; and the questions termlens declines to guess at are named.
• SECURITY.md no longer claims the emulator runs with zero
  scrollback. That sentence was the whole memory-bound argument in the
  resource-exhaustion note, and 0.4 made it false — the emulator is
  constructed with the configured history length. Every bound a child's
  output can reach is listed in its place: history length, retained frames,
  the read buffer, the OSC 52 capture cap, the reply queue, and the
  diagnostics set.

Documented

• The crate-level docs describe 0.4, not 0.2. The docs.rs landing page
  never mentioned wait_frame, retained scrollback, per-call deadlines or
  the clipboard accessor, so the crate's own front page understated it by
  two releases. It now names them, in the same breath as the guarantees
  that make them worth using.
• docs/DESIGN.md §2 records the per-call deadlines. The document that
  calls itself the contract for wait semantics had never mentioned the
  _for variants. It also now records the wait_idle timeout that names
  an unfinished frame instead of reporting silence against a quiet
  terminal.
• docs/HANDOFF.md is marked as the historical v0.1 record it is,
  rather than reading as a description of the project today — it described
  a private repository and an unfinished go-public checklist. The checklist
  keeps its original text, with the outcome recorded beneath it, including
  the one item resolved differently on purpose (required approvals stay at
  0: a solo maintainer cannot approve their own pull request).
• The announcement draft carried v0.1's limitations, two of which have
  since shipped; it now describes 0.4, and no longer claims to be untracked
  while sitting in the repository. The bug-report template no longer offers
  0.1.0 as its example version.

No library code changed in this release.