Enforce submodule-only AsyncTI4 data loading and add PR gate for pbd22635 analysis + unit tests

[Copilot]

The analyze workflow was partially loading data from non-repo locations, which caused missing datasets (notably hyperlanes) and fallback behavior that masked data integrity issues. This change makes data loading strict: all required datasets must come from the local AsyncTI4 submodule, or execution fails fast.

• Data source hardening (no partial fallbacks)

  • Added centralized submodule resource discovery in scripts/_data_paths.py.
  • Replaced brittle path assumptions (e.g., deriving from installed package location) with repository/submodule resolution.
  • Enforced hard errors when required data directories/files are missing or empty (technologies, leaders, planets, systems, attachments, units, hyperlanes).

• Removed incomplete/remote fallback paths

  • Removed strategy-card and strategy-card-set remote URL fallback logic.
  • Removed silent “return empty” fallback branches for required datasets.
  • Kept behavior aligned with requirement: local submodule data is the single source of truth.

• Workflow coverage for this regression

  • Added .github/workflows/pr-unit-tests.yml on pull_request to main.
  • Runs ti4-analyze "pbd22635" and then python -m pytest tests.

• Tests updated for strict behavior

  • Reworked strategy-card loader tests to assert local-data loading and hard failures when local data is absent.
  • Added new tests for hard-error behavior across tech, leader, planet, system, and hyperlane loaders.

# before: silently degraded
# except (OSError, ValueError):
#     return {}

# now: fail fast on missing/invalid required data
with _HYPERLANES_DATA_FILE.open(encoding="utf-8") as fh:
    ...