ci: Fix yamllint and actionlint issues in workflows and actions

[oxyzenQ]

• Add missing YAML document start markers (---) across all workflows and local actions
• Fix composite action metadata schema for install-nix and install-deps-action
• Update deprecated actions/checkout@v2 to v4 in scheduled workflows
• Resolve yamllint warnings: line length, comment indentation, truthy values
• Fix actionlint ShellCheck issues: quote variables, group redirects, wrap long commands
• Add affinitized/Affinitized to codespell ignore-regex as valid technical terms

All workflows and local actions now pass yamllint and actionlint cleanly.

Author: rezky_nightky
Repository: scx
Branch: main
Signing: GPG (4B65AAC2)
HashAlgo: BLAKE3

[ Block Metadata ]
BlockHash: 4c527f3f5c3bdcacdf8bf34f1b9492bd8d1ddbffa5f9bf39d86025197180a4c9 PrevHash: 2e9592a342db5f5bec7d7c45aa5e4b0e32fc90a97ea05287bc81d2a3845f09ab PatchHash: 40a977d46e8d641c486d7b8e09d74b74385833f91e277f2dd3d2ba53fa5d9a2c

FilesChanged: 9
Lines: +201 / -108

Timestamp: 2026-01-02T17:49:24Z
Signature1: 6e6df5e19976a2635f4e4d1a7a320f8856a22777340843095a4e2804b72eab1f
Signature2: 916c001496e30771d981b35874f6b50ff4a9e83bcf33c5afe6346132603d3999

[likewhatevs]

could you please rebase this, it's a bit stale?

will merge after, i'll be working on ci a bit soon.

[oxyzenQ]

could you please rebase this, it's a bit stale?

will merge after, i'll be working on ci a bit soon.

ok i will rebase.