Simplify batch/heex sources.json entries and parametrize alias tests

[Pringled]

Summary

• Drop the explicit "sources": ["src/parser.c"] for batch/heex — that's GrammarSpec.sources's own default, and matches the convention already used by other single-parser.c entries (json, go, c, java, etc.).
• Collapse the three near-identical alias tests (terraform/embeddedtemplate/zsh) into one parametrized test_aliases.

Test plan

• make test (92 passed), make lint, make typecheck all pass

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The omitted grammar source fields resolve to the same src/parser.c default, and the parametrized test preserves all three existing alias checks.

_{Reviews (1): Last reviewed commit: "Simplify batch/heex sources.json entries..." | Re-trigger Greptile}