feat(signals): add MinerGoalSpec type contract

[Helios531]

Summary

This PR implements #2293 by adding the initial type surface for .gittensory-miner.yml.
It defines the foundation-phase MinerGoalSpec contract and a safe DEFAULT_MINER_GOAL_SPEC, covering:

• minerEnabled
• wantedPaths
• blockedPaths
• preferredLabels
• maxConcurrentClaims
• issueDiscoveryPolicy

This PR is intentionally types-only. It does not add parsing, file discovery, or CLI wiring yet.

Related Issue

Closes: #2293

Change Type

• New feature
• Type contract
• Foundation work
• Test update
• Bug fix
• Database migration
• Docs-only change

Real Behavior Proof

Before

• There was no dedicated type contract for .gittensory-miner.yml
• Miner-goal config fields and defaults were not defined in a single typed module

After

• The repo has a dedicated MinerGoalSpec type
• The repo has a safe DEFAULT_MINER_GOAL_SPEC
• The issue-discovery policy reuses the same semantic vocabulary as the existing focus-manifest side
• Every field has a co-located default documented in JSDoc

Validation

• Focused unit tests passed
• Repo typecheck passed

Commands Run

npx vitest run test/unit/miner-goal-spec.test.ts
npm run typecheck

Key Files

• src/signals/miner-goal-spec.ts
• test/unit/miner-goal-spec.test.ts

Checklist

• MinerGoalSpec type added
• DEFAULT_MINER_GOAL_SPEC added
• Safe defaults documented
• Focused tests added
• Validation completed
• Branch pushed

[superagent-security]

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[loopover-orb]

Important

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.71%. Comparing base (17d70b2) to head (c4ec90b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2392   +/-   ##
=======================================
  Coverage   95.71%   95.71%           
=======================================
  Files         222      223    +1     
  Lines       24661    24662    +1     
  Branches     8949     8949           
=======================================
+ Hits        23605    23606    +1     
  Misses        433      433           
  Partials      623      623           

Files with missing lines	Coverage Δ
src/signals/miner-goal-spec.ts	100.00% <100.00%> (ø)

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[Helios531]

@JSONbored Could u plz review my PR?

[JSONbored]

@JSONbored Could u plz review my PR?

Stop tagging me for reviews, next time you'll wait +5 days for a review or be auto-closed.

[JSONbored]

This is a problem, closing.

The main maintainability risk is that the exported default contains mutable arrays, which future consumers can accidentally mutate as shared process state.