docs: run example snippets that were needlessly excluded from doc tests

[tomas-zijdemans]

This PR removes the ignore directive from 111 JSDoc example snippets that type-check, run, and pass as-is. They now execute as doc tests instead of sitting in the docs as dead code.

I audited all 370 ```ts ignore fences in the repo. Most earn their ignore: failing-assertion demos, Deno.serve on fixed ports, BDD examples that can't nest inside a doc test. These 111 don't. They're read-only, deterministic, and local. Things like walk("."), exists() checks, and the 42 console.log-only examples in cli/unstable_ansi.ts. Also resolves the TODO(iuioiua) in async/abortable.ts and async/unstable_abortable.ts, whose examples pass cleanly under --trace-leaks on current Deno.

Note for reviewers: 79 of these snippets don't assert anything, so check_docs.ts flags them once they lose ignore (that's what failed the first lint run here). Those fences are now ```ts no-assert: they still run as doc tests, the checker just knows the missing assertion is intentional. That's the whole diff on those lines.

Deliberately left ignored, for a possible follow-up:

• Anything fetching live URLs (offline CI would flake)
• Snippets reading stdin or piping to Deno.stdout.writable (pipeTo closes stdout)
• tar/tar_stream.ts examples that write out.tar.gz into the cwd
• Four fs/walk.ts followSymlinks examples that actually fail: walking . hits a broken symlink in fs/testdata/copy_dir_link_file/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (ad7c87b) to head (ea3fd22).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7242      +/-   ##
==========================================
+ Coverage   95.00%   95.03%   +0.02%     
==========================================
  Files         617      617              
  Lines       51674    51503     -171     
  Branches     9326     9283      -43     
==========================================
- Hits        49093    48944     -149     
+ Misses       2038     2023      -15     
+ Partials      543      536       -7     

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