fix: prevent statusline hook from hanging on stdin

[tbouquet]

Summary

Two fixes for abtop-statusline.sh that address #15:

1. Hang fix: replace INPUT=$(cat) with a read -r -t 5 loop — the script now times out after 5 seconds instead of blocking indefinitely when stdin isn't closed. Uses bash builtins only, works on both macOS and Linux (no coreutils dependency).

2. Large payload fix: pipe JSON to python via stdin (json.load(sys.stdin)) instead of passing it as a CLI argument (sys.argv[1]). Avoids hitting ARG_MAX on large status payloads and prevents breakage from special characters in the JSON.

Users need to re-run abtop --setup after updating to regenerate the hook script.

Fixes #15

Test plan

• Valid JSON input → writes correct abtop-rate-limits.json
• No rate_limits key → exits cleanly
• Empty stdin → exits immediately (no hang)
• /dev/null stdin → exits instantly
• cargo clippy -- -D warnings passes
• cargo test — 25/25 pass

[graykode]

Thanks for tackling #15! The approach is solid — read -t 5 for timeout and stdin pipe for ARG_MAX are both good calls. A few issues before merging:

1. echo "$INPUT" is unsafe — if the JSON contains \n, \t, -n, -e, echo may interpret them. Use printf '%s' "$INPUT" instead.

2. Newlines are stripped — INPUT="${INPUT}${line}" joins all lines without newline separators. If Claude ever sends pretty-printed JSON, json.load will fail on the concatenated string. Should be INPUT="${INPUT}${line}\n" or similar.

3. Minor: timeout is per-line, not global — read -r -t 5 resets the 5s timer on each line. Not a real problem for StatusLine payloads (usually one line), but worth noting.

Could you address 1 and 2?