Task: Import ORE trades onto the anchor alone

An ORE import writes only the anchor and its components; nothing in the import reads or writes the wide trade.

• The import item carries the anchor, the booking, the activity type and the ORE id; the planner fills them, and no import code names the wide trade.
• The import no longer writes the wide trade; the instruments still save against the anchor.
• A rollback closes the bookings of the trades the import booked, keyed by trade id; the immutable anchors stay.
• The import defaults that only the wide trade held (effective and termination date) are removed.
• The round trip stays at in-scope lost 0, with every envelope as stated; build, ctest and the local check set pass.

• Reshape trade_import_item around what the import books: the ORE id, the anchor, the booking and the activity type, beside the envelope, the instrument and the source file. The importer fills the ORE id and the trade type and leaves every id nil.
• Give the planner one helper that places a trade: it mints the id, sets the party and the book, stamps the instrument, and applies the defaults. The effective and termination date defaults go: no caller sets them and only the wide trade held them.
• Delete importer::validate_trade and the two trade_mapper::map overloads, which only built the wide trade, with their tests.
• In the execute handler, book from the item and stop writing the wide trade. A trade counts as saved once it is booked, and the result lists it by trade id.
• Rename the result's saved_trade_external_ids to saved_trade_ids. The rollback closes those trades' bookings, because the anchor is immutable: a trade with no live booking is off its book, and the export reads only live bookings.

Every number this task claims about a tree, with the command that produced it and the commit it was measured at. A number without both is not a measurement, because a clean-up record describes a tree and trunk moves under a branch: a consumer count, a gate's component count and a suite's size all change with no code changing, and the reader of a bare number cannot tell which tree it came from. Where the raw output matters, put it in an evidence/ file beside the task and name that file in the Command column.

Manual QA scenarios (scaffolded via compass add test_scenario) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

The ORE import carries each trade as its ORE id, anchor, booking and activity type, and books it without writing the wide trade. The planner places a trade through one helper; the effective and termination defaults, validate_trade and the wide trade_mapper::map overloads are gone. The result lists booked trades by id, and the rollback closes their bookings, leaving the immutable anchors. The merged portfolio round trip writes no wide trade, keeps in-scope lost 0 and returns every envelope as stated.