docs(miner-discovery): package.json test:mcp-pack + build:mcp parity checks for gittensory-miner

[JSONbored]

The existing packages/gittensory-mcp package has two CI guardrails that keep its publish shape honest: test:mcp-pack (scripts/check-mcp-package.mjs, verifying the published files list actually contains everything needed) and build:mcp (a node --check syntax-validation pass over the bin/lib/scripts files). packages/gittensory-miner (scaffolded in an earlier issue) needs the equivalent pair so a broken miner-package publish is caught in CI the same way a broken mcp-package publish already is.

Deliverables

• scripts/check-miner-package.mjs — copy scripts/check-mcp-package.mjs's structure and logic, retargeted at packages/gittensory-miner (verify package.json's files array covers every file actually needed to run bin/gittensory-miner.js, and that the declared bin path exists and is executable).
• Root package.json script "test:miner-pack": "node scripts/check-miner-package.mjs", mirroring the existing "test:mcp-pack": "node scripts/check-mcp-package.mjs" entry.
• Root package.json script "build:miner": "npm --workspace @jsonbored/gittensory-miner run build", mirroring the existing "build:mcp" entry (the package-level build script itself was added in the miner-scaffold issue).
• A unit test test/unit/check-miner-package.test.ts (mirror whatever test already exists for check-mcp-package.mjs, if one does — otherwise a small script-invocation test asserting the checker exits 0 on a well-formed package and non-zero on a files array missing a required path).

References

• scripts/check-mcp-package.mjs — the exact existing checker to copy/retarget
• root package.json scripts "test:mcp-pack" and "build:mcp" — the exact script-entry pattern to mirror for the miner package
• packages/gittensory-miner/package.json (from the miner-scaffold issue) — the package this checker validates

[linear-code]

JSO-2407