chore(ci): address all lint findings (#206)

This addresses a variety of findings, mostly around overly broad default
permissions and credential sharing.

I've also run [pinact](https://github.com/suzuki-shunsuke/pinact) to
auto-hash-pin all action references -- Dependabot will still update
these, but having them hash-pinned will seal off any undesirable
tag/branch mutability 🙂

(99% of these findings were done automatically with `zizmor --fix=all`,
followed by verifying the results. I haven't added a
[zizmor](https://docs.zizmor.sh) workflow as part of this PR, but I'd be
happy to if desired.)

---------

Signed-off-by: William Woodruff <william@astral.sh>

.github/workflows/update-known-checksums.yml

@@ -11,8 +11,10 @@ jobs:
       contents: write
       pull-requests: write
     steps:
-      - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          persist-credentials: false
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: "20"
       - name: Update known checksums