[kevin9327]

The CLI reads compression levels as 32-bit unsigned values and casts them to int, so a level between 2^31 and 2^32-1 wraps around to a negative (fast) level instead of being treated as "too high":

$ zstd -f -19 README.md -o b.zst -q            # 4815 bytes
$ zstd -f -3000000000 README.md -o a.zst -q    # 11850 bytes: (int)3000000000 is -1294967296, clamped to the fastest level
$ zstd -f -4294967295 README.md -o a.zst -q    # compresses at level -1
$ ZSTD_CLEVEL=+3000000000 zstd ...             # same wrap through the environment variable
$ zstd -f --adapt=max=4294967295 README.md     # accepted, max level becomes -1

-99 and ZSTD_CLEVEL=+99 are clamped to the maximum level (there is a test for it), and values above 2^32-1 are rejected, but the range in between silently selected a fast level.

Changes, all in programs/zstdcli.c:

• -# and the benchmark range -e# go through a new readCLevelFromChar(), which returns INT_MAX for a value above INT_MAX; the existing clamp then turns it into the maximum level, like -99.
• ZSTD_CLEVEL clamps the absolute value the same way before applying the sign.
• readIntFromChar() (used by --adapt=min=,max=) now rejects a value above INT_MAX with its existing "numeric value overflows 32-bit int" error, which it previously printed only above UINT_MAX. This also removes the signed overflow of (int)result * sign for -2147483648.

Tests:

• tests/cli-tests/compression/levels.sh: zstd -3000000000 and ZSTD_CLEVEL=+3000000000 must produce the same output as -19 (expected stderr updated). Fails on dev (the outputs differ), passes with the change; compression/levels.sh and compression/basic.sh pass with run.py.
• tests/playTests.sh: --adapt=max=4294967295 must fail (it exited 0 on dev; it now exits 1 with the overflow error). I checked this case by hand against both builds; I did not run the whole playTests.sh.

Built with gcc on Linux x86-64 (-DZSTD_MULTITHREAD -DZSTD_DISABLE_ASM).

AI disclosure (CONTRIBUTING rule 10): I used an AI assistant to help find this issue and write the change; I reviewed the code and ran the tests above.