Document MINER_CODING_AGENT_* env vars in the miner package's README and DEPLOYMENT.md

[JSONbored]

Context

The coding-agent driver (MINER_CODING_AGENT_PROVIDER, MINER_CODING_AGENT_CLAUDE_MODEL, MINER_CODING_AGENT_CODEX_MODEL, MINER_CODING_AGENT_TIMEOUT_MS) is already production-wired per the recently-merged driver construction work, but packages/gittensory-miner/README.md and packages/gittensory-miner/DEPLOYMENT.md never mention any of these four env vars. docs/coding-agent-driver.md documents the driver's internal interface, not operator-facing setup, leaving a real gap for anyone trying to configure a provider from scratch.

Dependencies

None — independently shippable. The underlying driver config is already live in the codebase, so this documentation reflects existing, shipped behavior rather than anticipating unshipped work.

Requirements

1. Add a new section to packages/gittensory-miner/README.md listing all four env vars: MINER_CODING_AGENT_PROVIDER, MINER_CODING_AGENT_CLAUDE_MODEL, MINER_CODING_AGENT_CODEX_MODEL, MINER_CODING_AGENT_TIMEOUT_MS.
2. For MINER_CODING_AGENT_PROVIDER, document the accepted values (noop/claude-cli/codex-cli/agent-sdk) and its default.
3. For each of the other three vars, document its purpose and default value.
4. Mirror the same section (or a cross-reference to it) in packages/gittensory-miner/DEPLOYMENT.md, since that's the file operators use during actual deployment setup.
5. Keep the framing operator-setup-focused ("how do I configure this"), distinct from docs/coding-agent-driver.md's interface-level documentation ("how does this work internally") — cross-reference that file rather than duplicating its content.
6. No code changes — this is a documentation-only PR.

Deliverables / Acceptance Criteria

• New env-var section added to packages/gittensory-miner/README.md
• Matching section (or clear cross-reference) added to packages/gittensory-miner/DEPLOYMENT.md
• All four env vars documented with accepted values/defaults where applicable
• Cross-reference to docs/coding-agent-driver.md added rather than content duplicated

Test Coverage Requirements

This PR must ship with full test coverage for every changed line and branch — the repo's Codecov patch gate requires 99%+ coverage and the house standard is to aim for 100%, including both sides of every conditional/nullish-coalescing branch introduced. Since this is a documentation-only change with no src/** lines touched, the Codecov patch gate itself will not apply meaningfully; instead add: (1) a lightweight drift-check test (or a documented manual verification step, if no test harness covers markdown content in this package yet) asserting the four env-var names as written in the docs actually match the names read in packages/gittensory-engine/src/miner/driver-factory.ts, (2) an invariant check that the documented default values match the code's actual defaults, and (3) no regression test is needed since this is not a bug fix.

Expected Outcome

An operator setting up gittensory-miner for the first time can find every coding-agent-driver env var, its accepted values, and its default in the README/DEPLOYMENT docs instead of having to read driver source code to discover them.

Links & Resources

• packages/gittensory-miner/README.md
• packages/gittensory-miner/DEPLOYMENT.md
• docs/coding-agent-driver.md (interface-level doc to cross-reference, not duplicate)
• packages/gittensory-engine/src/miner/driver-factory.ts (source of truth for var names/defaults)
• See Build production CodingAgentDriver construction + wire into the create phase #5131, feat(miner-governor): build production CodingAgentDriver construction (#5131) #5138 (the driver construction work this documents, already merged)
• See Update DEPLOYMENT.md to document all local stores #4870 (a distinct doc covering local stores, not these env vars)
• Theme: Claude/Codex self-host operational parity

[linear-code]

JSO-3709