fix(terminal): harden hydration lifecycle

[almogdepaz]

summary

• keep replacement terminal output hidden until authoritative hydration settles
• make container observation the single resize owner and preserve scroll intent
• bound slow viewer output and make resize/pty teardown terminal-ended states explicit
• preserve grapheme clusters and width-two cells in broker snapshots
• bump package version to 1.6.7

verification

• bun test (1,642 passing)
• focused playwright terminal suite (32 passing; 34 project-gated skips)
• broker cargo test (133 library, 25 socket, 6 fixture passing)
• typecheck passing

Docs, plans, reports, benchmark output, and generated local binaries are intentionally not included.