chore: pin our selected typescript version (5.0.4) to the top-level node_modules install to reduce duplication

[trentm]

PR #2856
(feat(deps): lock file maintenance) "decided" to move
[email protected] up to the top-level ./node_modules/... and move the
much more common [email protected] (the version we intentionally have
all published packages depend on) into the package-specific subdirs
(e.g. ./packages/{subdir}/node_modules/typescript).

This resulted in (a) a much bigger working copy after npm ci
(895M -> 3.7G!) and (b) a "WARNING" of unsupported typescript version
from running 'npm run lint' in a package dir.

---

See slack thread with some details: https://cloud-native.slack.com/archives/C08T7MZTV8W/p1754064934133129

I also have a theory (without too much evidence) that this could be contributing to CI being slow: the build-and-cache step in unit-test.yml has a WHOLE LOT MO build to cache.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.79%. Comparing base (e259677) to head (1a14add).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2988      +/-   ##
==========================================
- Coverage   89.82%   89.79%   -0.04%     
==========================================
  Files         188      188              
  Lines        9295     9295              
  Branches     1907     1907              
==========================================
- Hits         8349     8346       -3     
- Misses        946      949       +3     

see 2 files with indirect coverage changes

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