feat(cli): support reading JavaScript from piped stdin

[Nakshatra480]

Summary

This PR adds support for reading JavaScript from piped stdin in the CLI.

Currently, when no file or -e expression is provided, Boa always drops into the interactive REPL — even if stdin is being piped from another command. This means common workflows like these don't work:

echo 'console.log("hello")' | boa
cat script.js | boa
boa < script.js

Changes

Added a check using std::io::IsTerminal in main() to detect when stdin is not a terminal. When piped input is detected, the CLI reads the full input and evaluates it as a script instead of launching the REPL. The normal interactive REPL behavior is completely unchanged.

How it works

The detection happens after the existing file and -e checks, so the priority order is:

1. File arguments → execute files
2. -e expression → evaluate expression
3. Piped stdin (not a terminal) → read and evaluate stdin
4. Otherwise → launch the interactive REPL

Testing

# Simple expression
echo '1 + 2' | boa
# Output: 3

# console.log
echo 'console.log("hello")' | boa
# Output: hello

# Multi-line script
printf 'let x = 10;\nlet y = 20;\nconsole.log(x + y);' | boa
# Output: 30

# File redirection
boa < script.js

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,862	52,862	0
Passed	49,505	49,505	0
Ignored	2,261	2,261	0
Failed	1,096	1,096	0
Panics	0	0	0
Conformance	93.65%	93.65%	0.00%

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.05%. Comparing base (6ddc2b4) to head (c0ca9a7).
⚠️ Report is 704 commits behind head on main.

Files with missing lines	Patch %	Lines
cli/src/main.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4734      +/-   ##
==========================================
+ Coverage   47.24%   57.05%   +9.80%     
==========================================
  Files         476      552      +76     
  Lines       46892    60575   +13683     
==========================================
+ Hits        22154    34559   +12405     
- Misses      24738    26016    +1278     

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[Nakshatra480]

@nekevss i have implemented the feature that i discussed in the community channel, can you review this PR.
Thanks for your time.

[Nakshatra480]

Hey @nekevss @jedel1043 just following up here 🙂

These changes makes boa run JavaScript piped to stdin (for example echo '1+1' | boa or boa < script.js) instead of launching the REPL.

It detects non-terminal stdin with std::io::IsTerminal (after the existing file and -e checks), reads the piped input and evaluates it as a script, REPL stays the same when stdin is a terminal.

Would really appreciate a review. I’m happy to make any tweaks.
Thanks for your time

[nekevss]

Super cool addition! I actually really like it.

Can you add some examples of this functionality to the README.md for boa_cli so that this functionality is displayed somewhere.

[jedel1043]

Looks great!