docs(engine): goal-model.ts has zero TSDoc despite computeLaneFit being README-referenced

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Context

packages/loopover-engine/src/goal-model.ts has zero doc comments — no module header, no TSDoc on its one exported type (GoalModelInput) or its one exported function (computeLaneFit). This is unusual for the package: nearly every other module has at minimum a module-level header explaining scope and intent (compare miner-goal-lane-fit.ts in the same directory, which imports from this file and has three /** ... */ blocks for a smaller surface).

computeLaneFit is not obscure — it's referenced by name in packages/loopover-engine/README.md's "Metadata opportunity signals" section ("computeMetadataLaneFit — label-only lane fit by default; honors optional candidatePaths via computeLaneFit") without ever explaining what it does. A reader who follows that reference to the actual source finds no explanation there either.

The function's behavior is genuinely non-obvious and worth documenting precisely:

• blockedPaths/blockedLabels are a hard veto — any match against either returns 0 immediately, before wantedPaths/preferredLabels are even considered.
• If neither wantedPaths nor preferredLabels is configured, the result is a fixed neutral 0.5, not 0 or 1.
• If either is configured but neither actually matches, the result is 0.
• Otherwise the result is matchedDimensions / activeDimensions — i.e. partial credit when only one of two configured dimensions (paths vs. labels) matches.
• compileGlobMatcher implements its own glob semantics (*, **, **/, ?) rather than using an existing glob library — worth a one-line note on exactly what's supported, since a caller writing a wantedPaths/blockedPaths pattern in .loopover-miner.yml's MinerGoalSpec needs to know this.

Requirements

• Add a module-level header comment to goal-model.ts explaining its role: the pure lane-fit scorer that MinerGoalSpec's path/label preferences compile down to, consumed by miner-goal-lane-fit.ts and opportunity-metadata.ts's computeMetadataLaneFit.
• Add a TSDoc block on GoalModelInput explaining each field.
• Add a TSDoc block on computeLaneFit spelling out the exact precedence/scoring rules above (blocked = hard veto → no criteria = 0.5 → partial credit by matched/active dimension count), since callers need this to reason about scores, not just the return type.
• Add a short comment on compileGlobMatcher (or promote it alongside computeLaneFit's doc) noting which glob tokens are supported (*, **, **/, ?) and which aren't (e.g. character classes, brace expansion).

Deliverables

• Module header + TSDoc on GoalModelInput and computeLaneFit in packages/loopover-engine/src/goal-model.ts
• Short doc note on compileGlobMatcher's supported glob syntax

Test Coverage Requirements

Doc-comment-only change — no new executable lines or branches, so it does not add to the src/**/packages/loopover-engine/src/** patch-coverage surface Codecov measures. The existing packages/loopover-engine/test/goal-model.test.ts suite must stay green (run npm test --workspace @loopover/engine and npm run test:coverage locally — this file is inside coverage.include, so if a doc-comment edit accidentally reformats/removes an existing line it would still need re-verifying).

Expected Outcome

computeLaneFit's exact scoring behavior (hard-veto, neutral-default, partial-credit rules) is documented at its own definition site, not left implicit in the implementation or referenced-but-unexplained from the README.

Links & Resources

• packages/loopover-engine/src/goal-model.ts (the file to change)
• packages/loopover-engine/src/miner-goal-lane-fit.ts — a caller, and an example of this package's TSDoc style
• packages/loopover-engine/src/opportunity-metadata.ts — computeMetadataLaneFit, the other caller
• packages/loopover-engine/README.md's "Metadata opportunity signals" section — where computeLaneFit is referenced by name today
• packages/loopover-engine/test/goal-model.test.ts — existing test coverage to cross-check the documented rules against

[linear-code]

JSO-4003