fix release workflow: use softprops/action-gh-release for latest tag

[cs01]

Summary

The `install.sh` download URL returned 404 after PR #497 merged because the `latest` release ended up stuck in draft state with its tag disconnected from any commit (URL was `/releases/tag/untagged-aae38c13828ddbf9ef52`). Manually re-published it to unblock users.

Root cause: the `release` job's two-step "delete old release with `--cleanup-tag`, then create new release" pattern has a race condition. If the tag cleanup hasn't propagated by the time `gh release create latest` runs, the new release is created in a partial state — no tag attachment, ends up as draft. The `|| true` on the delete step hid any signal that this happened, so the job still reported success.

Fix

Replace the two-step delete/create with a single `softprops/action-gh-release@v2` step. The action talks to the GitHub Releases API directly and handles the create-or-update-by-tag flow atomically — no race window. The `tagged-release` job in the same file already uses this action, so this brings both release paths in sync.

• Drops 20 lines, adds 9.
• Explicit `tag_name: latest`, `make_latest: "true"`, and `target_commitish: ${{ github.sha }}` so the tag always attaches to the commit that triggered the workflow.

What users see

• `curl -fsSL https://raw.githubusercontent.com/cs01/ChadScript/main/install.sh | sh` stops failing with a 404 on the next merge to main.
• No change for tagged releases (`v*`) — that job was already using softprops and is untouched.

Test plan

• CI green on this PR
• After merge, check that the `release` job on main produces a published (non-draft) release at `/releases/tag/latest` with all four tar.gz assets
• `curl -sI https://github.com/cs01/ChadScript/releases/download/latest/chadscript-macos-arm64.tar.gz\` returns 302 after the next main merge

[github-actions]

Benchmark Results (Linux x86-64)

Benchmark	C	ChadScript	Go	Node	Bun	Place
Binary Trees	1.643s	1.257s	2.733s	1.266s	1.091s	🥈
Cold Start	0.8ms	1.0ms	1.2ms	29.9ms	10.4ms	🥈
Fibonacci	0.908s	1.417s	1.732s	3.369s	2.072s	🥈
File I/O	0.091s	0.095s	0.091s	0.175s	0.207s	🥉
JSON Parse/Stringify	0.004s	0.005s	0.016s	0.014s	0.007s	🥈
Matrix Multiply	0.489s	0.739s	0.782s	0.428s	0.418s	#4
Monte Carlo Pi	0.439s	0.440s	0.457s	2.591s	6.491s	🥈
N-Body Simulation	1.750s	2.252s	2.290s	2.406s	3.333s	🥈
Quicksort	0.246s	0.283s	0.242s	0.296s	0.261s	#4
SQLite	0.327s	0.377s	—	0.411s	0.401s	🥈
Sieve of Eratosthenes	0.014s	0.027s	0.020s	0.042s	0.039s	🥉
String Manipulation	0.010s	0.044s	0.015s	0.044s	0.031s	#4

CLI Tool Benchmarks

Benchmark	ChadScript	grep	node	xxd	Place
Hex Dump	0.429s	—	0.983s	0.141s	🥈
Recursive Grep	0.022s	0.012s	0.102s	—	🥈