feat: Add JLCPCB component import for LCSC part numbers

[paycheckpacheck]

Summary

Adds support for importing JLCPCB/LCSC parts as circuit-synth components. Until now the JLCPCB integration could search for parts and print a code snippet, but there was no supported way to go from an LCSC part number to a Component object with the sourcing data attached.

New module: src/circuit_synth/manufacturing/jlcpcb/component_import.py.

Public API

from circuit_synth.manufacturing.jlcpcb import import_jlc_component

r1 = import_jlc_component("C25804")
# Component(symbol="Device:R", ref="R", value="10K",
#           footprint="Resistor_SMD:R_0603_1608Metric",
#           LCSC="C25804", MPN="RC0603FR-0710KL", Manufacturer="YAGEO",
#           JLCPCB_Stock="956234", JLCPCB_Part_Type="Basic")

• import_jlc_component(lcsc_part, ref=None, symbol=None, footprint=None, value=None, **properties) -> Component - look up an LCSC part number and build the component.
• component_from_search_result(result, ...) -> Component - build a component from an existing FastSearchResult without performing another lookup (works with cached results).
• lookup_lcsc_part(lcsc_part) -> Optional[JlcPartSpec] - non raising lookup for callers that want to fall back to a locally specified component.
• JlcComponentImporter - injectable class holding the search backend and the KiCad mapping provider; resolve_part(), spec_from_search_result(), spec_from_catalog_entry(), build_component(), import_component().
• JlcPartSpec - resolved part data with to_properties() and to_circuit_synth_code().
• normalize_lcsc_part() and the error hierarchy JlcImportError -> JlcPartNotFoundError, JlcLookupError, SymbolResolutionError.

Symbol, footprint, value and reference prefix are resolved through the existing SmartComponentFinder mappings, whose lookup helpers are now public methods (find_kicad_symbol, find_kicad_footprint, reference_designator_for, is_passive_component, extract_component_value) instead of being duplicated.

Component properties attached: LCSC, MPN, Manufacturer, JLCPCB_Package, JLCPCB_Price, JLCPCB_Stock, JLCPCB_Part_Type (Basic or Extended). Properties without data are omitted.

CLI

jlc-fast import C25804            # resolved part data plus the Component definition
jlc-fast import C25804 --json     # machine readable output
jlc-fast import C999999 --symbol Device:R

Degradation behavior

• Search backend exceptions are wrapped in JlcLookupError, so an unavailable or rate limited JLCPCB endpoint does not surface as an arbitrary exception; lookup_lcsc_part() returns None and logs a warning.
• No exact catalog match raises JlcPartNotFoundError (the CLI reports it and exits with status 1).
• A missing footprint mapping logs a warning and still produces a component.
• A missing symbol mapping raises SymbolResolutionError unless symbol= is supplied.

Testing

38 new tests, all with the JLCPCB search layer mocked, so no network access is required:

• tests/unit/jlc_integration/test_jlc_component_import.py (33 tests) - part number normalization, symbol/footprint/value resolution for passives and ICs, property mapping, code generation, lookup success and failure paths, component construction, overrides and fallbacks.
• tests/unit/tools/test_jlc_fast_search_cli.py (5 tests) - the new CLI command including the unknown part and unmapped symbol paths.

$ pytest tests/unit/jlc_integration tests/unit/test_fast_jlc_search.py \
         tests/integration/test_fast_jlc_integration.py tests/unit/tools
189 passed, 3 skipped, 2 warnings in 4.25s

The 3 skips are the pre-existing network dependent JLCPCB integration tests. black and isort report no changes on the touched files.