chore: remove compatibility with .meta file

[dkharms]

Description

We no longer support .meta files which were completely substituted with .wal files. This pull request removes all support for .meta file and backwards compatibility mechanisms.

---

• I have read and followed all requirements in CONTRIBUTING.md;
• I used LLM/AI assistance to make this pull request;

If you have used LLM/AI assistance please provide model name and full prompt:

Model: {{model-name}}
Prompt: {{prompt}}

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.95652% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.74%. Comparing base (59fdb2b) to head (c13d7fc).

Files with missing lines	Patch %	Lines
frac/active.go	86.66%	1 Missing and 1 partial ⚠️
cmd/seq-db/seq-db.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #462      +/-   ##
==========================================
+ Coverage   70.48%   70.74%   +0.26%     
==========================================
  Files         232      231       -1     
  Lines       18269    18163     -106     
==========================================
- Hits        12876    12849      -27     
+ Misses       4432     4356      -76     
+ Partials      961      958       -3     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.