Build production CodingAgentDriver construction + wire into the create phase

[JSONbored]

Problem: createCodingAgentDriver/runCodingAgentAttempt (packages/gittensory-engine/src/miner/driver-factory.ts:155,217) have zero production caller anywhere in packages/gittensory-miner — confirmed by grep: every reference outside the definition and its re-export (packages/gittensory-engine/src/index.ts:316,321) is a test or doc comment. packages/gittensory-miner/lib/coding-agent-house-rules.js:11 states this explicitly in its own header. This is the "create" phase of the loop — actually invoking a coding agent to write code in a worktree — and it has no live entrypoint, independent of whether the CLI dispatch itself is wired (see #B).

Area: AMS / Miner

Proposal: Wire a real, CLI-config-driven driver-construction call site, mirroring the existing SelfHostAi/AI_PROVIDER seam pattern already used elsewhere in this codebase (per the original Phase 3 design), so attempt-runner.js (and its future CLI dispatch) can receive a real CodingAgentDriver as an injected dependency instead of only ever seeing test doubles.

Deliverables:

• A real driver-construction module invoked from a production code path (not only from tests), producing a working CodingAgentDriver from local config.

Acceptance criteria:

• A real (non-test-injected) invocation constructs a working driver and it successfully drives at least one coding-agent turn against a scratch worktree.
• Existing driver-factory.ts unit tests pass unchanged.

Resources:

• packages/gittensory-engine/src/miner/driver-factory.ts (the existing seam — reuse, don't redesign).
• packages/gittensory-miner/lib/coding-agent-house-rules.js (PreToolUse hook enforcement this driver must respect once wired).

Boundaries:

• Wiring only — the driver abstraction itself already exists and is tested. Do not redesign the seam.

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Part of #5130.

[linear-code]

JSO-3679