fix(copy): say "Making room" and "Permissions" in Engine messages

[Hmbown]

No-Issue: applies the ratified product vocabulary to Engine messages; no public issue.

CURRENT_DECISIONS §19 (ratified 2026-09-22) names the user-facing words:
"Making room" for summarizing earlier conversation, not
compaction/auto-compaction, and "Permissions" rather than posture. The
Engine's compaction, preview, turn-loop and /compact messages still
used the old words.

Mined from the unreviewed 0.10.1 WIP branch (copy-only hunks in 16
files; its unrelated session-restore hunks in the same files are left
for their own slice). Two corrections to the WIP:

• The emergency failure "could not bring the request under the model
  limit" would have dropped from an Error to an Info toast, because
  toast severity is classified from the wording. It now reads "Making
  room failed: the request is still over the model limit …", which keeps
  the Error level.
• test_compact_toggles_state still expected the old word; updated to
  the ratified copy (history: §19 decision, not a regression).
  Model-facing prompt text, config keys and the /compact command name
  are unchanged.

Evidence: 1799 passed, 1 failed (the missed copy assertion above) across
compaction, preview, core::engine::tests, commands::,
session_acceptance, launch_resume_tests and app::status selections;
after the fix 31/31 session_lifecycle_regression_tests passed. TUI
all-target/all-feature Clippy with CI flags and fmt passed.

🤖 Generated with Claude Code

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