Keep ANSI colors out of pretty transport lines (#375)

[terehov]

Fixes #375 for the 5.2.0 release.

On an interactive terminal the pretty line handed to attached transports carried the console's ANSI escape codes, so a fileTransport on a pretty logger wrote color codes into the log file (the same for HTTP, ring-buffer and custom sinks, and for an explicit format: "pretty"). It only came out clean when stdout was piped, because pretty.style follows the console's TTY.

Change

• The pretty() format stage (the only path transports use) renders from a copy of the settings with style: false, so a transport's pretty line is always plain text. The copy includes inspectOptions, so the logger's own settings and console colors are untouched.
• The tslog CLI pretty-printer calls prettyFormatLine directly and keeps coloring on a TTY.
• Regression tests in tests/41_issue_fixes.test.ts: an attached transport on a styled logger, an explicit format: "pretty", and an end-to-end fileTransport run matching the report. All fail against the old code; one also guards that console styling survives.
• README transport section, llms.txt, RECIPES §10 and the 5.2.0 changelog note that transport pretty lines are always plain.

Browser bundle grows ~40 B gzip, within the 22,400 B budget.

Verified locally: Node (1678 tests, 100% coverage), Bun, Playwright on Chromium, build, bundle size, doc-sync, and the reporter's setup under a real pseudo-terminal.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (99875bf) to head (e90396c).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #376   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           53        53           
  Lines         4628      4632    +4     
  Branches      1361      1381   +20     
=========================================
+ Hits          4628      4632    +4     

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