feat(weir): add SameExact rule to catch redundant "same exact"

[jlaportebot]

Summary

Adds a Weir rule that flags the redundant phrase same exact, since same already implies exactness. Suggests same alone.

Why this rule?

• Redundancy: "same exact" is tautological — if two things are the same, they are necessarily exact.
• Asymmetry: The inverse "exact same" is a valid emphasis pattern (e.g., "the exact same thing"), so this rule only targets "same exact" which lacks the emphasis justification.
• Common mistake: "same exact" appears frequently in informal writing.

Changes

• New SameExact.weir rule with test cases and allows guards
• Added to default_config.json (alphabetical order)
• Added to VS Code plugin package.json

Test coverage

• 6 positive tests (catches "same exact" → "same")
• 2 case-preservation tests (Title Case, UPPER CASE)
• 5 negative tests (allows "exact same", "same" alone, etc.)

All 69 weir tests pass, including curated_default_config_lists_every_registered_rule.

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

If Your PR Implements or Enhances a Linter

• I made up the sentences in the unit tests.
• The sentences in the unit tests were generated by an AI.
• I'm using examples from the bug report / feature request.
• I collected real-world sentences for the unit tests.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.