refactor(tx-manager): make nonce manager generic over provider trait

[jackchuma]

What changed? Why?

Makes NonceManager generic over a provider trait (P: Provider) instead of being hardcoded to RootProvider.

• NonceManager now takes a type parameter P and stores provider: P instead of provider: RootProvider
• The impl block is bounded by P: Provider, so any provider implementation can be used
• SimpleTxManager concretizes the type as NonceManager<RootProvider> to preserve its existing API
• RootProvider import moved from the main module to the test module where it's still needed for the test-only seeded constructor

This decouples the nonce manager from a specific provider type, enabling easier testing with mock providers and reuse in contexts that don't use RootProvider.

Notes to reviewers

Pure refactor — no behavioral changes. All existing tests pass without modification (only type annotations updated).

How has it been tested?

Existing unit and integration tests in crates/utilities/tx-manager/ continue to pass.

Change management (definitions)

type=routine
risk=low
impact=sev5

Backwards Compatibility (learn more)

backwards_compatible=true

automerge=false

[linear]

CHAIN-3471 Make NonceManager generic over Provider trait

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
base	Ignored		Mar 17, 2026 1:15am

[github-actions]

Review Summary

Clean refactor — no issues found.

The change correctly introduces a generic parameter P: Provider on NonceManager, replacing the hardcoded RootProvider. Key observations:

• Bounded correctly: P: Provider on the impl block, no unnecessary bounds on the struct definition (idiomatic Rust).
• Derive implications: #[derive(Debug, Clone)] implicitly requires P: Debug + Clone, which is a natural requirement for provider types and is satisfied by RootProvider.
• Scope is minimal: SimpleTxManager remains concrete with NonceManager<RootProvider> — no over-generification.
• All references updated: Verified no external crate references to NonceManager were missed.
• Test helpers properly scoped: new_with_nonce narrowed to impl NonceManager<RootProvider>.