chore: enable no-node-globals and no-process-global lint rules

[tomas-zijdemans]

Enables the no-node-globals and no-process-global lint rules proposed in #7251. Both already pass: deno lint reports zero violations across 1169 files, so this is a config-only change.

Type checking doesn't reliably catch a bare process or Buffer. Any npm dependency can pull @types/node into the type graph, and from that point the reference type-checks silently. _tools/check_browser_compat.ts skips tests and _-prefixed files by design. The lint rules close that gap for every file, on every PR.

The ban-untagged-todo part of #7251 comes as a separate PR, since it touches code.

I used Claude Code to help investigate and write this change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (ca58f94) to head (95e70f5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7292   +/-   ##
=======================================
  Coverage   95.03%   95.03%           
=======================================
  Files         617      618    +1     
  Lines       51637    51640    +3     
  Branches     9359     9359           
=======================================
+ Hits        49075    49078    +3     
  Misses       2021     2021           
  Partials      541      541           

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