forward and reverse inherited characteristics

[matt-beanland]

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[matt-beanland]

Summary

• Closes path shelf characteristic #10 (turtles down — path brings up its card, port, and transitively its shelf via the port-then-slot assignment chain) and calculations and aggregates #32 (turtles up — shelf brings up its cards in slot order and aggregates total port capacity).
• Adds three local calculation modules: InheritedCharacteristic (incoming traversal — assignee inherits from assigner), ReverseInheritedCharacteristic (outgoing traversal — assigner brings up its assignees; "insanity is hereditary, you get it from your kids"), and Access.Calculations.ShelfTotalPorts (multi-hop aggregate-style calc).
• Aliases on assignments are the assignee's slot names — set via %Assignment{alias: :port, ...} (path-as-assignee) and %Assignment{alias: :slot, ...} (card-as-assignee) in the path-test helper. Existing tests without aliases stay unchanged.
• Yarned upstream as inherited_characteristic + reverse_inherited_characteristic — bring up typed characteristic values across the assignment graph diffo#172 (DSL declarations: inherited_characteristic, reverse_inherited_characteristic) and JSON surfacing of inherited (and reverse-inherited) characteristics, places, parties diffo#173 (JSON surfacing of inherited and reverse-inherited concepts). The local calc modules are working reference implementations ready to lift.

What landed

Calc modules

• DiffoExample.Calculations.InheritedCharacteristic — mirrors Diffo.Provider.Calculations.InheritedPlace; traverses incoming AssignmentRelationship by alias, then reads the typed characteristic value from each source instance.
• DiffoExample.Calculations.ReverseInheritedCharacteristic — dual; traverses outgoing AssignmentRelationship (optionally alias-filtered), reads the typed characteristic on each assignee.
• DiffoExample.Access.Calculations.ShelfTotalPorts — domain-specific calc summing AssignableCharacteristic.(last - first + 1) across each card a shelf has assigned a slot to.

Resource shape

• Card — new :shelf calc (brings up shelf characteristic via via: [:slot]) and :slot calc (assigned slot value).
• Path — new :card calc (via: [:port]), :shelf calc (via: [:port, :slot], two-hop), :port calc (assigned port value).
• Shelf — new :cards calc (brings up assigned cards in slot order) and :total_ports calc (aggregate).

Tests

• path_test updated to set aliases on slot and port assignments in create_dslam_with_line_card; new assertions verify path.card, path.shelf, path.port resolve through the two-hop chain.
• shelf_test adds new "shelf brings up its cards and total_ports" test asserting two cards (48 ports + 24 ports = 72 total) resolve through the outgoing traversal.

Test plan

• mix test — 49 tests, 0 failures
• mix format — clean
• reuse lint — 96/96 files compliant
• Manual: Ash.load(path, [:card, :shelf, :port]) returns the expected brought-up values through the assignment chain
• Manual: Ash.load(shelf, [:cards, :total_ports]) returns cards in slot order and the correct port-capacity sum

Notes for reviewers

• JSON rendering of inherited values isn't included in this PR — that's the diffo#173 yarn. The calcs work at the Ash API level (Ash.load + Ash.read); TMF JSON surfacing waits for the upstream DSL+JSON enhancement so we don't add per-resource customize that becomes dead code.
• Alias discipline: the assignee names its own slot. Existing tests with multiple unaliased assignments to the same target (e.g. two pairs to one service) work as before; the new path-test scenarios set aliases explicitly because the calcs need them to traverse by name.