refactor(cli): extract provider commands into commands/provider module

[varshaprasad96]

Summary

• Extract all provider-related functions, helpers, constants, structs, and tests (~2,700 lines) from the monolithic run.rs into a dedicated commands/provider.rs module
• Add pub use re-exports in run.rs so main.rs requires zero changes — all call sites continue using run::provider_create(...) etc.
• Clean up unused imports in run.rs (provider proto types, openshell_providers, dialoguer::Confirm, HashSet, etc.)

Related Issue

Part of #2304 — CLI refactor series PR3 (provider commands). PRs 1–2 (scaffolding + gateway) are merged.

Changes

File	Change
crates/openshell-cli/src/commands/mod.rs	Add pub mod provider;
crates/openshell-cli/src/commands/provider.rs	New — 2,671 lines: 24 public functions/structs, 27 private helpers/constants, 22 tests
crates/openshell-cli/src/run.rs	Remove ~2,700 lines of provider code, add re-exports, clean unused imports

Not changed

• main.rs — all calls go through run:: re-exports, no changes needed
• No behavioral changes — pure mechanical code move with visibility adjustments

Testing

• cargo check -p openshell-cli — zero errors, zero warnings
• cargo test -p openshell-cli — all 211 tests pass (22 provider tests running from new location under commands::provider::tests)
• mise run pre-commit — all lint, format, and license checks pass
• Verified all 22 pub use re-exports match the 19 call sites in main.rs plus internal cross-module usage

Checklist

• Follows Conventional Commits format
• Follows the extraction pattern established in PR2 (gateway.rs)
• DCO sign-off included
• No AI attribution in commits
• Pre-commit checks pass

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