fix: avoid redundant Nautilus completion pass

[Jammy2211]

Overview

Nautilus factor searches that converge in their first call still trigger an intermediate result update and a second no-op sampler call. Remove this overhead, following the completed Dynesty EP optimisation in #1642.

Plan

• Recognize convergence immediately while preserving finite-budget updates.
• Cover convergence, chunked execution and likelihood limits with regression tests.
• Compare sampler/update calls, seeded results and timing, then run the full PyAutoFit suite serially.

Detailed implementation plan

• Repository: PyAutoFit; clean main, no competing claim. Existing hook-maintenance branch does not overlap.
• Branch: feature/ep-nautilus-single-pass.
• Inspect the installed Nautilus run completion contract and likelihood counter before selecting the completion condition.
• Update autofit/non_linear/search/nest/nautilus/search.py (Nautilus.call_search, and budget handling if required). Do not infer likelihood budget exhaustion from posterior sample counts.
• Extend test_autofit/non_linear/search/nest/test_nautilus.py with converged and finite-cadence cases, global limits and a seeded real-search comparison. No public API change intended.
• Validate targeted tests and full serial test_autofit; measure overhead without changing sampler settings or EP mathematics.

Original user request

We have begun a task speeding up the PyAutoFit source code to make EP run faster without PyautoFit overheads, continue this task

The human approved this bounded follow-up after explanation: “ok, do it.”

Existing prompt

PyAutoMind/draft/bug/autofit/nautilus_converged_run_double_pass.md records the redundant completion pass and the requirement to preserve finite-cadence sampling.

[Jammy2211]

Implementation is complete in feature/ep-nautilus-single-pass (base 69bb11d54, source edits not yet committed). Nautilus uses its own convergence return, advances cumulative budgets using n_like, and stops at a global cap even if a batch overshoots it.

Validation:

• Full serial PyAutoFit suite: 2934 passed, 2 skipped (300.23 s).
• Nautilus tests: 16 passed; all 8 new regression cases fail against the original methods.
• Real fits with seeds 13 and 14: 2 → 1 sampler calls, 1 → 0 intermediate updates, posterior parameters/likelihoods/weights bit-identical.
• Instrumented intermediate update removed: 68–75 ms/search. Total timing is noisy; no end-to-end percentage speedup claimed.
• Autofit workspace smoke: 8/8 scripts, 2/2 notebooks passed in isolated disposable checkouts. Wider smoke stopped during environment preparation after the shipping gate below.

Fresh Heart tick (2026-09-29T19:22:53Z) is RED:

PyAutoFit: 1 commit(s) behind origin
PyAutoLens: 1 commit(s) behind origin

These refer to canonical checkouts; the task branch is based on current PyAutoFit origin/main. Awaiting a human development-only override or cleared Heart before commit/push/PR. No merge or release requested. Detailed local evidence paths and resume instructions are in the Mind prompt's handoff.

[Jammy2211]

The live human authorized the named #1651 development override and same-turn merge: "yeah, and then do a $prm".

Exact Heart RED reasons previously surfaced:

• PyAutoFit: 1 commit(s) behind origin
• PyAutoLens: 1 commit(s) behind origin

Passed branch gates: 2934 tests passed / 2 skipped serially; 16 Nautilus tests passed; 8 autofit workspace scripts + 2 notebooks passed; seeded posterior samples/likelihoods/weights bit-identical. The broader downstream smoke run has resumed. No release or CI/protection bypass is authorized; merge remains conditional on every required CI run and matrix leg passing.

[Jammy2211]

Downstream smoke validation

All eight configured workspace groups passed against this task's PyAutoFit source, using pyauto-heart smoke and isolated disposable workspace checkouts.

Workspace	Scripts passed	Notebooks passed	Failed
autofit	8	2	0
autogalaxy	14	2	0
autolens	41	2	0
autolens_test	32	0	0
euclid	9	0	0
howtolens	50	0	0
autocti	3	0	0
autocti_test	3	0	0
Total	160	6	0

CTI environments used the documented no-root GSL extraction into task scratch; no system packages changed. Full log: .worktrees/ep-nautilus-single-pass/smoke-resume.log; workspace JSON reports: .smoke-root/*/test-results/ within that task.

Source validation remains 2934 tests passed / 2 skipped; all 8 new regression cases fail against the original methods. The human's named Heart RED development override and same-turn /prm authorization remain recorded above; no release is authorized.

[Jammy2211]

Shipped. Merged in #1652 (merge 5cf687d, 2026-09-30): a converged single-chunk Nautilus fit no longer runs a second no-op run() pass with a during_analysis update. Pending the next PyAutoFit release.