test(agent): add generated interface mocks

[rice-riley]

Description

Adds reproducible Mockery tooling and generated test doubles for the interfaces used by the final Go agent orchestration layer.

• Adds an agent-specific Mockery configuration for config validation, history, interrupts, and steps.
• Pins Mockery and exposes make generate-mocks through the component toolchain.
• Checks in generated testify mocks and the required module dependencies.
• Replaces the hand-written schema-validator fake with the generated mock.

Depends on #407.
Part of #219

Checklist

• I am familiar with the Contributing Guidelines.
• My commits are signed off (git commit -s) per the DCO.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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📝 Walkthrough

Walkthrough

Added Mockery tooling and Testify dependencies. Added generated mocks for SchemaValidator, Store, Interrupt, and Step. Updated the schema-validation test to use MockSchemaValidator instead of a local fake implementation.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested reviewers: lockwobr, ayuskauskas

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely identifies the addition of generated interface mocks for agent tests.
Description check	✅ Passed	The description accurately summarizes the Mockery tooling, generated mocks, dependencies, and test fake replacement.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent-mocks-219

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@agent/go/deps.mk`:
- Line 23: Add `unexport MOCKERY_VERSION` immediately after the
`MOCKERY_VERSION` assignment in the Makefile, keeping the variable available for
Makefile expansion while preventing it from being passed to Mockery’s
environment.

In `@agent/go/Makefile`:
- Around line 66-69: Update the generate-mocks target to ensure newly generated
mocks receive the repository’s Apache SPDX license header, since make fmt does
not process untracked files. Configure Mockery with the repository-managed
boilerplate file via .mockery.yaml or run addlicense on the generated mock paths
after $(MOCKERY) completes, while preserving the existing formatting step.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

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Run ID: 8cc963a8-4e89-45a1-94ce-f76b76734d9a

📥 Commits

Reviewing files that changed from the base of the PR and between d8efce7 and 2772b92.

⛔ Files ignored due to path filters (1)

• agent/go/go.sum is excluded by !**/*.sum

📒 Files selected for processing (9)

• agent/go/.mockery.yaml
• agent/go/Makefile
• agent/go/deps.mk
• agent/go/go.mod
• agent/go/internal/config/mock/SchemaValidator.go
• agent/go/internal/config/validate_test.go
• agent/go/internal/history/mock/Store.go
• agent/go/internal/interrupts/mock/Interrupt.go
• agent/go/internal/step/mock/Step.go

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[coderabbitai]

Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

The merge-base changed after approval.