[access-github-consumers] - Migrate repository and persistence token callers

[JoshuaRowePhantom]

Part of #1512 and master #1505

Parent

• Direct parent: [access-secrets-github] - Track stored-secret environment and GitHub executor slices #1512.
• Architecture master: [access-broker] - Unify credential-use authorization, acquisition, renewal, and presentation #1505.

Dependencies

• Depends on: [access-github] - Implement approved environment and gh CLI token executor #1541.

Summary

Move repository and persistence GitHub token consumers to IAccessBroker without changing their domain behavior.

Current Limitation / Root Cause

EntityRepository and the persistence source factory construct synchronous/static token delegates.

Affected Files

Path	Change
Phantom.Workspaces/EntityRepository.cs	Implement the bounded production change owned by this issue.
Phantom.Workspaces/Services/AgentPersistenceStoreSourceFactory.cs	Implement the bounded production change owned by this issue.
Focused test file	Add only the tests listed below.

Design / Fix

This slice implements the following exact contract:

public sealed class EntityRepository
{
    private ValueTask<TResult> UseGitHubCredentialAsync<TResult>(
        Func<string, CancellationToken, ValueTask<TResult>> operation,
        CancellationToken cancellationToken);
}
public sealed class AgentPersistenceStoreSourceFactory
{
    public Task<IAgentPersistenceStore> CreateAsync(
        CancellationToken cancellationToken);
}

Each repository or persistence operation submits its own purpose/requester request and disposes the result. No synchronous token resolver remains in these files.

Use required-init properties and named object initializers. The commit must build and its focused tests must pass without relying on a second implementation slice landing in the same commit.

Security and Privacy Invariants

• Release/use authorization occurs before material access or provider interaction whenever this slice can reach either boundary.
• No token, secret value, OAuth state, verifier, authorization URL, signed URL, device code, callback, account name, unsafe identifier, or credential-bearing result enters UI-safe state, logs, notifications, entities, or persistence.
• Typed results remain caller-owned and disposable; provider/cache artifacts remain executor-owned.
• Errors are typed and sanitized; no broad catch or success-shaped fallback is introduced.

Exclusions

• No batch API, compatibility bridge, legacy-data migration, silent interactive renewal, or unrelated provider work.
• No production types beyond the bounded files/classes named here.
• No UI work unless this issue is explicitly a UI slice.

Commit Plan

Commit 1 — [access-github-consumers] - Migrate repository and persistence token callers

Production scope: Phantom.Workspaces/EntityRepository.cs, Phantom.Workspaces/Services/AgentPersistenceStoreSourceFactory.cs.

Tests: GitHubCredentialConsumerTests methods listed below.

Acceptance: one small coherent commit; no opportunistic adjacent migration.

Expected Tests

Test Name	Class	What It Verifies
EntityRepository_GitHubOperation_UsesBrokerCredentialLease	GitHubCredentialConsumerTests	Verifies the named contract and leaves adjacent slices independently testable.
AgentPersistenceStoreSourceFactory_GitHubSource_UsesBroker	GitHubCredentialConsumerTests	Verifies the named contract and leaves adjacent slices independently testable.