Document the new `gittensory-miner mcp` tool surface in the package README and coding-agent-driver docs

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Context

This batch adds a set of read-only MCP tools under a new gittensory-miner mcp bin entry — covering a portfolio dashboard, claims, an event-ledger audit feed, governor decisions, run-state, and plan-store tools — but packages/gittensory-miner/README.md and docs/coding-agent-driver.md currently document neither the mcp bin entry nor any of these tools. Existing docs like DEPLOYMENT.md's local-stores section (#4870) and the README's storage table (#4876) describe where AMS stores its data, not how to reach it over MCP, so there is a real, current documentation gap once these tools ship.

Dependencies

This issue must land AFTER the AMS MCP server scaffold (the gittensory-miner mcp bin entry) and after at least one or two of the read-only tool PRs in this batch (e.g. the event-ledger audit-feed tool, the governor-decisions tool, the run-state tool, or the plan-store tools) actually exist in the codebase. Do not start this issue purely from issue descriptions — write the docs against the real, merged tool implementations and their actual parameter/response shapes. Treat this issue as blocked until at least the scaffold plus one or two tool PRs are merged.

Requirements

1. Add a new section to packages/gittensory-miner/README.md documenting the gittensory-miner mcp bin entry: how to start it, and that it is a local, read-only MCP server exposing the miner's own state.
2. For each read-only tool that has landed by the time this PR is written (portfolio dashboard, claims, event-ledger audit feed, governor decisions, run-state, plan-store, status/driver), document: the tool's name, what it returns (fields), and that it is read-only/metadata-only.
3. For the ledger/governor tools specifically, explicitly state which columns are intentionally excluded (e.g. that the governor-decisions tool never exposes payload_json) so the documentation itself reinforces the safety property.
4. Add a short paragraph clarifying how these local AMS MCP tools relate to the existing hosted gittensory-mcp tools — same naming conventions, different backing store (local SQLite vs. hosted), and that AMS's tools are scoped to the local miner instance only.
5. Cross-reference this new README section from docs/coding-agent-driver.md with a short pointer/link — do not duplicate the content there.
6. Do not document any tool that has not actually landed yet — keep the doc scoped to what's merged at PR time; add remaining tools in follow-up doc PRs as they ship, rather than describing unimplemented tools.
7. This PR must not change any code behavior — documentation only, no source changes.

Deliverables / Acceptance Criteria

• New "MCP tools" section added to packages/gittensory-miner/README.md
• Each landed tool documented: name, return fields, read-only/metadata-only note
• Explicit note on intentionally-excluded columns for the ledger/governor tools
• Paragraph relating AMS's local MCP tools to the hosted gittensory-mcp tools
• Cross-reference link added in docs/coding-agent-driver.md
• No undocumented/unlanded tools described
• No source code changes in this PR

Test Coverage Requirements

This is a documentation-only change with no src/** lines touched, so the Codecov patch-coverage gate does not apply in the usual sense. In lieu of unit tests, this PR must still ship with verification appropriate to a docs change: (1) confirm every tool name, file path, and parameter documented in the README actually exists in the codebase as merged (manually cross-check against the real tool registrations, not the issue descriptions), (2) an invariant check — manual or scripted — that every tool documented in the README also exists in the MCP server's tool registry at merge time, so docs and code cannot silently drift, and (3) no regression test is needed since this issue is not a bug fix.

Expected Outcome

A contributor or operator setting up the gittensory-miner mcp server can read one authoritative doc describing every available read-only tool, its output shape, and how it relates to the hosted gittensory-mcp surface, instead of piecing it together from individual PR diffs.

Links & Resources

• packages/gittensory-miner/README.md
• docs/coding-agent-driver.md
• See Update DEPLOYMENT.md to document all local stores #4870 (DEPLOYMENT.md local-stores doc — related but distinct)
• See Update the README's "Local storage" table #4876 (README storage table — related but distinct)
• See the sibling issues in this batch: event-ledger audit feed, governor decisions, run-state, and plan-store tools
• Theme: MCP exposure

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JSO-3699