forge.json run may be a compound command: cd sub && bun server.ts starts #10308

A run such as cd softwear/app && bun server.ts now starts as written. It no longer fails with exec: cd: not found. The same fix is applied to tty. The new tests, test/apps.test.ts, bun scripts/gate.ts and tsc pass here. I ran only the tests that cover this change. I did not use keep_plan to keep a plan on the issue.

• How it works: a new module, src/apps/run_command.ts, decides how a command is spawned. A simple command is still run with exec, so signals reach the app directly. A command containing &&, ||, ;, |, &, (), backticks, $(, or a newline is run as written, without exec. process.ts and tty.ts both use it.
• Stopping: I didn't change the stop logic. The no-cell case stops the whole process group. The cell case already walks the process tree. The new test starts cd sub && bun server.ts, checks it answers, stops it, and checks the port is closed.
• Start-failure line: when the shell says exec: X: not found, the failure message gets a hint. For a shell builtin like cd, it says to chain it with a program, as in cd sub && bun server.ts. For anything else, it says the program isn't installed or isn't on PATH.
• Tests: test/apps-compound-run.test.ts covers four things: the compound/simple split, the hint wording, a compound run starting, answering and stopping cleanly, and the hint appearing on a real start failure. The cell case isn't covered, because cells are skipped in this sandbox, so the forge's own check is the first to run it.

I did not add a dir field to forge.json or change the builder brief. The issue offered either route, and the compound command satisfies "the original string works" with less to maintain.

Commands that merely contain an operator inside quotes, like bun x --flag "a;b", count as compound and run without exec. They still work, but the shell stays as the app's parent process.

Closes #10294

A run such as cd softwear/app && bun server.ts now starts as written. It no longer fails with exec: cd: not found. The same fix is applied to tty. The new tests, test/apps.test.ts, bun scripts/gate.ts and tsc pass here. I ran only the tests that cover this change. I did not use keep_plan to keep a plan on the issue.

• How it works: a new module, src/apps/run_command.ts, decides how a command is spawned. A simple command is still run with exec, so signals reach the app directly. A command containing &&, ||, ;, |, &, (), backticks, $(, or a newline is run as written, without exec. process.ts and tty.ts both use it.
• Stopping: I didn't change the stop logic. The no-cell case stops the whole process group. The cell case already walks the process tree. The new test starts cd sub && bun server.ts, checks it answers, stops it, and checks the port is closed.
• Start-failure line: when the shell says exec: X: not found, the failure message gets a hint. For a shell builtin like cd, it says to chain it with a program, as in cd sub && bun server.ts. For anything else, it says the program isn't installed or isn't on PATH.
• Tests: test/apps-compound-run.test.ts covers four things: the compound/simple split, the hint wording, a compound run starting, answering and stopping cleanly, and the hint appearing on a real start failure. The cell case isn't covered, because cells are skipped in this sandbox, so the forge's own check is the first to run it.

I did not add a dir field to forge.json or change the builder brief. The issue offered either route, and the compound command satisfies "the original string works" with less to maintain.

Commands that merely contain an operator inside quotes, like bun x --flag "a;b", count as compound and run without exec. They still work, but the shell stays as the app's parent process.