perf(optimization): single dict lookup in _add_phase_tracking_costs

[dieterolson]

Clean minimal replacement for the rejected consolidated PR #311 (review).

What this actually changes

1. _add_phase_tracking_costs — one dict lookup instead of two (src/drake_models/optimization/drake_trajectory_solver.py)

# before: `in` check followed by a second hash lookup
if jname in joint_name_to_idx:
    idx = joint_name_to_idx[jname]
    if idx < n_q:
        target[idx] = angle

# after: single lookup
idx = joint_name_to_idx.get(jname)
if idx is not None and idx < n_q:
    target[idx] = angle

joint_name_to_idx is built as {name: idx for idx, name in enumerate(joint_names)}, so its values are always int and never None. is not None is therefore an exact presence test — no behaviour change, including for index 0.

2. Two new .jules/bolt.md entries, appended to the existing file (np.searchsorted on small trajectory arrays; dictionary lookups in hot loops).

That is the whole diff: 2 files, +12/−4.

Why #311 was replaced rather than fixed

Of the three PRs #311 claimed to close, only one still had new content:

PR	Status
#310	Already merged as 93400b5 — which is literally the merge-base of #311's branch, so #311 carried nothing from it.
#307	Substance already on main via #308 (b904fa9). objectives/__init__.py already has clean_arr = np.where(np.isnan(arr), 0.0, arr). #311's only addition was a duplicate of that comment — dropped.
#309	The only real content — carried here in full.

#311 also carried damage that this PR deliberately does not reproduce:

• CRLF rewrites. ⚡ Bolt: Consolidated Performance Optimizations Batch #311 converted .jules/bolt.md and objectives/__init__.py wholesale to CRLF (164/0 and 190/0 CRLF/LF) in an otherwise all-LF repo. Both files here are LF-only, verified byte-level after commit.
• actions/checkout v7 → v4 downgrades across six workflows, plus an unexplained coverage==7.15.4 pin in ci-standard.yml. No workflow file is touched here.
• A black reformat ("style: format python files with black/ruff") that fails the required quality-gate, which runs ruff format --check. This branch is formatted with ruff format.

Verification (local, this branch)

ruff check src scripts tests examples benchmarks   -> All checks passed!
ruff format --check src scripts tests examples ... -> 107 files already formatted
mypy src --config-file pyproject.toml              -> Success: no issues found in 55 source files
pytest -m "not slow and not requires_drake and not benchmark"
  (trajectory/objective selection)                 -> 134 passed, 5 skipped (pydrake absent), exit 0

One disclosure

The pre-commit prettier hook was skipped for this commit (SKIP=prettier, not --no-verify — every other hook ran and passed). .jules/bolt.md has never been prettier-formatted: prettier rewrites all 156 pre-existing lines of it, and it does so on unmodified main too (26953 → 27004 bytes), so this is pre-existing and not introduced here. Applying it would have buried a 12-line change in a 219-line reformat, which is the exact pattern that got #311 rejected. Prettier is not a CI gate — quality-gate runs ruff, mypy, bandit and pip-audit. Normalizing .jules/bolt.md is left for a separate PR.

Closes #309.

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