smith: add PTY prompt flag default-on; gate EditorState; fix duplicate insertion; WIP isearch to follow

[edwin-zvs]

This PR makes the smith PTY line editor/UI behave better in interactive PTY mode and lays groundwork for incremental isearch:

• Introduce CONSTRUCT_SMITH_PTY_PROMPT (default on) and emit the initial prompt; keep TUI/editor gated in PTY mode
• Fix duplicate character insertion by always redrawing after inserts; recompute slash-ghost each edit
• Normalize CRs on submit so multi-line prompts round-trip
• Cap history at 10,000 entries and de-dup consecutive identical lines
• Ctrl-L now only clears/redraws the bottom prompt/completions region
• Add reset_history(), tighten history navigation and queued recall behavior

Follow-ups:

• Incremental search (C-r) for history; buffered UTF-8 input decoding for non-ASCII

Testing:

• Manually exercised PTY keystrokes (Enter, Ctrl-L, arrows, Home/End, Backspace, Del, Tab-complete)
• cargo build on macOS (debug) across the workspace; adapter-smith compiles cleanly

Notes:

• Only crates/adapter-smith is functionally changed in this PR; CLI/daemon warnings are pre-existing.