feat: improve REPL interface with banner, dot-commands, and --quiet flag

[sahanaxzy]

Summary

Improves the REPL experience by adding a welcome banner, dot-commands, and a --quiet flag.

Solves #4883

Changes

• Welcome banner with version info on startup
• .help, .clear, .load <file> dot-commands
• --quiet / -q flag to suppress the banner
• Ctrl+C now shows exit hint instead of quitting
• Improved error formatting (bold + red labels)
• Added help descriptions for -O and --optimizer-statistics
• Updated README.md with new REPL Commands section

Files Changed

Modified cli/src/main.rs

REPL loop, banner, dot-commands, CLI flags, error formatting

Modified cli/README.md

Updated CLI options and added REPL Commands section

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	49,666	49,666	0
Ignored	2,284	2,284	0
Failed	1,013	1,013	0
Panics	0	0	0
Conformance	93.77%	93.77%	0.00%

Tested main commit: 1753d9729e3d0930d808990f6911ca0b940a21d7
Tested PR commit: bda50ee6fec6c325240b42f0ec1f241f8ee713a9
Compare commits: 1753d97...bda50ee

[hansl]

I'd be okay with a TODO comment in the code for the second point and doing it in a follow up PR.

[hansl]

Just wanted to add, I like this a lot and I think it goes into the right direction. I look forward to having a more powerful REPL.

[sahanaxzy]

cc @hansl Addressed both points — trimmed readline input and added TODO for CliCommand enum. Please re-review, thanks!

[sahanaxzy]

@hansl The CI failed on formatting, so I pushed a quick rustfmt fix. Could you please re-approve the workflows?

[codecov]

Codecov Report

❌ Patch coverage is 0% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.67%. Comparing base (6ddc2b4) to head (bda50ee).
⚠️ Report is 773 commits behind head on main.

Files with missing lines	Patch %	Lines
cli/src/main.rs	0.00%	50 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #4888       +/-   ##
===========================================
+ Coverage   47.24%   57.67%   +10.43%     
===========================================
  Files         476      556       +80     
  Lines       46892    60782    +13890     
===========================================
+ Hits        22154    35057    +12903     
- Misses      24738    25725      +987     

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[hansl]

@sahanaxzy Please fix the linting errors and I'll reenable CI + merge.

[jedel1043]

you might need to merge pull the latest changes

[sahanaxzy]

Thanks! I’ve pulled the latest changes from main and updated the branch.