Fix UUID case-sensitivity issue in registry lookup

[arnavk23]

• Normalize registry package UUIDs to lowercase for matching
• Fixes issue where packages with uppercase UUIDs in Registry.toml were incorrectly identified as not registered
• Add test for registry with uppercase UUIDs
• Fixes Getting a This package is not registered, skipping with Plots, no new tag #483

[Copilot]

Pull request overview

This PR fixes a UUID case-sensitivity issue in registry lookup where packages with uppercase UUIDs in Registry.toml were incorrectly identified as not registered.

• Normalizes registry package UUIDs to lowercase for case-insensitive matching
• Adds comprehensive test coverage for the fix

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tagbot/action/repo.py	Implements case-insensitive UUID matching by converting registry package keys to lowercase before lookup
test/action/test_repo.py	Adds test case verifying that uppercase UUIDs in the registry are properly matched with lowercase UUIDs from the project

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[IanButterworth]

Seems reasonable but where's the problematic UUID?
https://github.com/JuliaRegistries/General/blob/0a1a6078b38f2420ae5b7ae26b8f5b021a1e2dee/Registry.toml#L7503

[arnavk23]

Seems reasonable but where's the problematic UUID? https://github.com/JuliaRegistries/General/blob/0a1a6078b38f2420ae5b7ae26b8f5b021a1e2dee/Registry.toml#L7503

Looking at the actual issue #483: Plots.jl failed to match during registry lookup despite being registered. The fix ensures UUID comparison is case-insensitive by normalizing both the project UUID (line 273) and all registry package UUIDs (line 307) to lowercase before comparison. Even though the current registry snapshot may be entirely lowercase, the issue likely occurred because Plots.jl's Project.toml had a UUID with different casing than the registry keys, causing the case-sensitive dictionary lookup to fail silently.

[IanButterworth]

Yeah, I'm wondering where it was capitalized. That issue is recent. We should be able to figure it out.