docs: fix typos and improve documentation

[cookingypq]

Description

This PR fixes various documentation issues and improves code quality:

• Fix grammar error in README.md: "ecosystem consist" → "ecosystem consists"
• Fix syntax error in CONTRIBUTING.md: "to an open issue" → "to open an issue"
• Complete TODO section in poly/README.md with comprehensive domain documentation
• Fix broken GitHub links in test-templates and bench-templates README files

The most critical files to review are:

• README.md (main project documentation)
• CONTRIBUTING.md (contribution guidelines)
• poly/README.md (polynomial library documentation)

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• Targeted PR against correct branch (master)
• Linked to GitHub issue with discussion and accepted design OR have an explanation in the PR that describes this work.
  • Note: This is a documentation-only PR fixing typos and improving docs, no design discussion needed
• Wrote unit tests
  • Note: Documentation changes only, no code changes requiring tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md
  • Note: Documentation improvements don't require changelog entries
• Re-reviewed Files changed in the GitHub PR explorer