Avoid calling get_prompt() unless needed

[rolandwalker]

Description

Since some prompt escapes are expensive, and can even require a trip to the server, avoid calling get_prompt() unless needed, preferring to use the cached value in the last_prompt_message property, or a new saved value for the number of lines in the prompt.

Incidentally, explicitly strip ANSI formatting from prompts before writing them to a file, when tee is in effect.

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .

[github-actions]

1. Regression: tee now splits prompt and query onto separate lines

• In run_cli, prompt and SQL are written via two write_tee() calls (main.py:1167, main.py:1168).
• write_tee() always appends a newline per call (iocommands.py:444), so entries change from "<prompt><query>\n" to:
  • "<prompt>\n"
  • "<query>\n"
• This is a behavior change and likely unintended for tee logs/readability/parsing.
• Action: write prompt+query in a single call (after ANSI stripping), or add a newline=False option for prompt writes.

2. Regression risk: cached prompt_lines is not invalidated when prompt shape changes

• prompt_lines is set once and reused (main.py:1380); get_prompt_message() only updates it when zero (main.py:924).
• After \R prompt changes, DB changes (\u), or host/db length changes crossing default_prompt split threshold, line count can change but cache stays stale.
• This can miscompute pager-fit decisions via get_output_margin().
• Action: recompute prompt_lines whenever prompt is regenerated, or reset cache on prompt/db/connection changes.

3. Missing tests for the new behavior

• Existing tests cover basic write_tee("hello world"), but not ANSI prompt input nor prompt+query composition (test_special_iocommands.py:68).
• Action: add tests for:
  • write_tee(ANSI(...)) strips escapes.
  • interactive tee log keeps prompt+query formatting as expected.
  • get_output_margin() updates after prompt format/database changes.

No new security issue stood out in this PR.

[scottnemes]

get_prompt is called slightly less, but barely. So technically works.

Hitting enter 5 times causes 153 calls to get_prompt prior to this, and 152 calls with this.

Various other tests resulted in an average of 3-5 call difference. So major room for future improvement if that can be reduced.

[rolandwalker]

Ah, so something is still very wrong.