fix(interceptors): keep shell positionals, a late --, and option values

[moise10r]

What this changes

memnox-shell dropped the words after the -c line and switched to argv mode on a -- that came after -c. It also ran pipefail in -o pipefail -c cmd as if it were a script. The parser now reads arguments left to right. -o, +o, -O, +O, --rcfile and --init-file take their value with them. The new commandShellArgs passes $0, $1 and "$@" to the real shell unchanged.

How it was verified

packages/interceptors/test/shell-line.test.ts has a parser test for each of the three forms in the issue. Another test runs /bin/sh with what commandShellArgs returns and checks the output.

Fixes #15

Checklist

• pnpm format && pnpm typecheck && pnpm test && pnpm deadcode all pass
• Behaviour change ships with a test
• No any, no magic values, no console.* outside cli-output.ts
• If this touches the decision path: still deterministic — no LLM, network, or randomness
• If this changes a verb table: the classes that moved are named above (not applicable)
• If this changes a command, flag or file it writes: docs/ says so (not applicable)