Changes touching this path

• adding one opt-in perf half stops costing thirteen hand-edits and starts costing two, because Fixtures keys its opt-in halves by the OPT_IN_HALVES row that already described them instead of ten Option<Workload> fields with three constructors re-listing every None, and loot-perf-gate builds its whole valued-flag set and both its usage strings out of that same table, so the hand-typed [&str; 17] arity is gone and a throwaway row the strict parse refused by name before this change is accepted with no second edit after it (#1599) Subsumes #1474, whose done-bar is the whole claim and was run in both directions before anything else. A throwaway half written the old way, with all eleven structural sites edited, was still refused by the shipped binary as an unknown argument --throwaway at exit 2, which is the #1465 experience live. After this change the same half is one contiguous row in OPT_IN_HALVES, and the binary accepts the flag, prints it in the derived usage line as [--throwaway <files>], and carries on past the parse to the pin stage. What moved: - Fixtures now holds one [Option<Workload>; OPT_IN_HALF_COUNT] array in OPT_IN_HALVES order rather than ten Option<Workload> fields. gated / split / uniform stop re-listing every None; with_X, the X() accessor and the free take_X function become Fixtures::with, Fixtures::half and OptInHalf::take, all keyed by OptInHalf::slot. - OptInHalf::of and OptInHalf::take, both fn pointers, become one Axis field. Axis is #847s rule written as data: the flag carries the half own axis and the other dimension is pinned in the row, so the ten one-line take_X functions that each re-implemented that rule are gone and a reader can see which dimension is which without leaving the table. - loot-perf-gate VALUED_FLAGS array, with the hand-typed [&str; 17] that walked 13 to 17 across five halves in one night, becomes valued_flags(): the union of RESIZES_A_HALF, TOUCHES_NO_FIXTURE and the table. The union is the point, because #1403 distinction is that --counters and --timing resize a half the gate already takes while an opt-in flag adds one. Both USAGE copies are derived too: the const becomes usage(), formatted from each row flag and axis word, and the module-doc synopsis enumerates no half at all. - OPT_IN_HALF_COUNT is OPT_IN_HALVES.len(), so no count of the halves is typed by hand anywhere. The invariant did not move, verified by running the gate rather than by reading it. An unflagged dry run of a release binary built from this tree prints workload counters=small_files/200+timing=small_files/2000+negotiation=small_files/24x96, carries no opt-in metric, and reports perf: no move against its baseline. A flagged run takes --compressible, --open and --graph-load together and produces compressed_read, repo_open and graph_load in their own batches under the id tail +compressed=compressible_files/64+open=small_files/200+graph_load=small_files/200x16, which is one row per Axis variant and both axis directions. New pins, each broken before being trusted: - every_half_takes_the_fixture_it_always_did writes out all ten halves workload ids at one flag value, because this is a refactor and a fixture id is the key #607 selects baselines on. Swapping the two dimensions of Axis::Changes reddens it with the value, small_files/64x200 against small_files/200x64. - taking_one_half_takes_exactly_that_half and no_two_halves_share_a_flag_or_an_id_key cover the slot keying over every ordered pair; a slot() that always answered 0 reddens both with values. - a_flag_moves_its_own_axis_and_pins_the_other makes the claim ten per-half tests each made by hand, once over the table and in both directions. - the_module_doc_synopsis_enumerates_no_half inverts the assertion #1436 wrote: that one held a hand-kept copy equal to the table, this one holds the copy to not existing. - every_valued_flag_is_classified_exactly_once replaces the old classification test, which is now true by construction, with what derivation cannot give: that the three classes are disjoint and their union is the whole set. Adding --reps to RESIZES_A_HALF reddens it. No assertion that OPT_IN_HALF_COUNT equals the table length is written, and a comment says why: it is that length, so no edit could redden it, and a check that cannot fail is worse than no check (#1578). 8e0284b8 · dbf3dbe6…

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