b6b12619

By: ValentinHirschi <valentin.hirschi@gmail.com>

Temporary official Nix workspace graph verification

Isolate the current metadata inputs and run the existing official Nix graph
generator twice to verify its fixed point. This scratch branch is not an
ALL_GREEN milestone, a complete feature snapshot, or a PR candidate.

User request (verbatim):

Assign yourself the goal in:
```
./HANDOFF_REMOVE_FOR_PR/HANDOFF_GOAL.md
```

which instructs you to start things off by fixing:
```
./HANDOFF_REMOVE_FOR_PR/HANDOFF_T2_DISCREPANCY.md
```

Note that this is a hard problem in a complicated code, so use subagents to compartimentalise the work and context and work systematically towards fixing the bugs.

Also read all contents of the folder `./HANDOFF_REMOVE_FOR_PR` to benefit from all the existing research already performed by a weaker agent.

Useful commands here in general are `output standalone --json` to be able to see expressions used in plain sight, and also `uv_profile` to test proper subtraction of UV singularities and of course various temporary edits of the code or custom tests to dissect problematic expressions to find MREs of them facilitating the understanding of the issues

Checkpoint and continuation instruction (verbatim):

Continue as planned and make sure that we can get `just test_gammaloop` complete without skipped test and within 30 GB of RAM. Once all green continue with the plan, and also the audit/review/refactor of the code related to local UV CTs from 3D and 4D as it is complicated and needs to be extremely clean, understandable, with the right amount of factorization, without any legacy hack, some comments where it's hard to understand, so as to make its future maintenance and extensions easier.
Make sure this clean version with green test is pushed with "ALL_GREEN" on the remote and the continue and complete the goal with the study of ddx and ttx.

Don't let my need for approval stop you again. If you must take a decision that you think is within the scope of my approval, triple-check that you really need it (not like point 2. before) and then choose the answer for yourself, and just write it in "PENDING_APPROVALS.md" and continue. I'll periodically come and ask you about that file's content, but no longer wait for me, just make a decision and proceed towards the goal completion.

Requested scalar target (verbatim):

Continue as planned, but I want you to add to the justfile a new target for `just test_LU_scalar_xs` (with `--release` compilation by default), which would match exactly the run you're doing now.

Requested fail-fast behavior (verbatim):

(ah and also in --fail-fast mode on this target).
Scalar generation optimization instruction (verbatim):

Continue as planned, but what are you doing now, can you try to finish the scalar LU matrix?
Also if you can find anyway to reduce the RAM usage and increase generation speed of these scalar cross-section you should do it now. while you wait for result. You had a pending study and proposal for an improvement that you can now look into (since we now know that `just test_gammaloop` is all green).
Explicit summed function-map request (verbatim):

I think that it may be faster to have the scalar matrix run with `summed_functionmap = false`, it will speed up the 3D direct route, and the runtime performance is irrelevant for this test.

Timeline