Support bun run stdin execution and argv semantics

Parent: #66 Follows completed publish corpus milestone #185.

Tracks the sorted untouched corpus boundary in cli/install/bun-run.test.ts.

Root cause

Home's real run argument scanner treated a lone - as an ignorable runtime flag. home run - therefore skipped its entrypoint and started the REPL instead of consuming stdin.

Scope

• recognize - as the stdin entrypoint before generic runtime flags
• read stdin with Bun's approximately-1-GiB ceiling and surface read errors
• execute stdin as a virtual [stdin] TypeScript module through the full native VM
• preserve relative resolution from cwd and process.argv === [exe, "-", ...args]
• model the same pipeline semantics in the Bun shell corpus runtime
• gate the complete untouched bun-run.test.ts result

Acceptance

• real printf ... | home run - smoke prints expected JavaScript output
• TypeScript stdin executes through the native VM
• stdin script arguments retain - in process.argv
• untouched bun-run.test.ts: 291 passed / 0 failed / 0 unsupported / 1 upstream TODO
• full home_test gate passes
• commit lands on main and #66 is updated

Landed

• e248d15c4 feat(cli): support bun run stdin
• Related resolver hardening: #188

Landed on main in e248d15c4.

Final verification:

• untouched cli/install/bun-run.test.ts: 291 passed / 0 failed / 0 unsupported / 1 upstream TODO
• native JavaScript stdin: hello
• native TypeScript stdin: 42
• native argv: [home-debug, "-", "alpha", "beta"]
• full zig build test -Dfilter=home_test --summary failures: exit 0
• Zig format and git diff --check: clean

The file-specific Bun shell hardcode is gone; the harness now models stdin-run pipelines through a reusable helper, while the actual CLI consumes stdin through the full VM as virtual [stdin] source.

The full gate also exposed and drove the focused cross-host resolver fix in #188.