feat(solve): aggregate interface transmission limits (RESOLVE CAISO import/export caps) (CPUC stack 3/5)

[ktehranchi]

Part of the CPUC/SERVM California stack (independent of #796; consumed by the CA config in stack PR 4/5).

Changes proposed in this Pull Request

Rewires the previously-dead config pair model_topology.interface_transmission_limits (gate) and electricity.transmission_interface_limits (path to repo_data/config/policy_constraints/transmission_interface_limits.csv) into a live constraint:

• workflow/scripts/opts/interfaces.py — per CSV row and direction, a per-snapshot cap on the sum of import/export Link flows crossing the interface: flow_21 caps imports into region_1, flow_12 caps exports out of it (orientation corroborated against known CAISO↔NW limits: CA_NW flow_12 = 3,592 MW matches the ~3.6 GW CAISO→NW export capability). Links are selected by bus membership + carrier, never by name parsing; external {zone}_imports buses are excluded from the inside-region set (they carry country=<zone>, which would otherwise leak them in via get_region_buses).
• Gated call in solve_network.py extra_functionality; the CSV is declared as an input on solve_network and solve_network_validation.
• Rows with no matching links log and skip, so the constraint is inert on networks without trade links or without the named zones.

Known, documented understatement: entries in region_2 that are inside the modeled network (e.g. p8 in a CA-only run) contribute no trade links, so internal AC lines (p8↔p9, ~300 MW) escape the links-only cap.

Testing

• Tier A pytest -m fast: 195 passed, 1 pre-existing skip (combined stack).
• New tests: test_interfaces.py — 6 passed (GLPK), including a binding-import-cap solve and a no-op run over the real shipped CSV.
• Tier B not run for this PR. No equivalence run for this branch (constraint is dormant unless model_topology.interface_transmission_limits: true, which no shipped config sets until stack PR 4).

Checklist

• I tested my contribution locally and it seems to work fine.
• pre-commit and pytest -m fast pass locally.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to workflow/envs/environment.yaml (no dependency changes).
• Changes in configuration options are added in workflow/repo_data/config/config.default.yaml (keys already existed; behavior documented in stack PR 4's configtables/prose updates).
• Changes in configuration options are also documented in docs/source/configtables/*.csv (arrives with stack PR 4).

🤖 Generated with Claude Code

[ktehranchi]

CI note: the fast-tests failures here are environmental, not from this diff — every failure is AssertionError: Solver glpk not installed (plus one downstream Optimization failed), hitting pre-existing test_policy/test_reserves cases that this PR does not touch (#796's diff is purely additive and fails identically). The CI workflow was re-enabled today after a long disabled period, and the runner environment for Tier A lacks the GLPK binary; there is no green develop baseline yet. Tier A passes locally with GLPK: 195 passed, 1 pre-existing skip. The e2e-tests failure is likewise infra ("Setup micromamba" step). Leaving the CI environment fix to the maintainers / the #794 CI work rather than folding it into this stack.

🤖 Generated with Claude Code

[ktehranchi]

Superseded by #801 — the five-PR stack was collapsed into a single PR at the author's request. All commits (plus Tier B fixes) are on feat/cpuc-servm-california.