The softplus leisure floor keeps leisure strictly positive in every
state-action cell, so the `positive_leisure` feasibility constraint never
binds. Remove it from the canwork retiree/nongroup/tied regime builders and
delete the unused `positive_leisure` helper; feasibility is now carried by
the smooth floor in the leisure functions themselves.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

BQSEGM solves one 1-D consumption/savings regime with at most one
discrete action, so unlike DC-EGM it attaches per regime: solver="bqsegm"
gives the M1 slice regime nongroup_nomc_inelig_canwork a BQSEGM config
(budget node `resources`, post-decision `savings`, the savings form
shared with DC-EGM) and leaves every other living regime on brute force.
The three savings-form gates in _common accept "bqsegm" alongside
"dcegm"; the HIS builders attach whichever EGM solver is present.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

The BQSEGM case-piece envelope handles at most one discrete action, so
the M1 vertical slice drops buy_private as a choice and binds it to
BuyPrivate.yes in its consumers (premium, OOP) via the dags
remove-and-fix convention. The brute and DC-EGM paths keep buy_private
as an action. The drop_labor_supply hook is added for the next step
(the pure-continuous slice also fixes labor_supply).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

The pure-continuous M1 slice drops labor_supply as a discrete action and
supplies it as a fixed full-time node (LaborSupply.h2000) read by labor
income, AIME accrual, and the lagged-supply transition. lagged_labor_supply
stays a state so the cross-regime continuation space is unchanged; the
nomc regime's lifecycle transition is unaffected (it never gated on labor).
With buy_private already fixed, the M1 regime now has no discrete action,
so the only choice is continuous consumption against the cliffed budget.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

…tax cliff

The M1 vertical-slice regime `nongroup_nomc_inelig_canwork` carries `assets`
(the Euler axis) alongside `aime` and the stochastic shock grids, so the BQSEGM
config names `continuous_state="assets"`; the rest ride along. The progressive
federal income tax is declared as a piecewise-affine schedule on `gross_income`,
kinking at each finite bracket edge `income_tax_schedule.brackets_upper[
spousal_income, k]`, so BQSEGM differentiates the budget per declared bracket.
The decorator is metadata-only — brute and DC-EGM solve identically.

With these the full model constructs under `solver="bqsegm"` (M1 via BQSEGM,
every other living regime on brute force).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

DC-EGM solves every living regime, so its solver-contract functions and the
dropped borrowing constraint are broadcast model-wide. BQSEGM solves only the
M1 regime, so broadcasting them forced every brute regime to supply the
solver's `marginal_continuation` and stripped their borrowing constraint.

Keep the model-level broadcast for DC-EGM only. The M1 regime carries the
savings-form budget functions (`resources`, `savings`) at regime level and
masks the borrowing constraint — BQSEGM enforces the borrowing limit through
its savings grid's lower bound. BQSEGM inverts the Euler equation internally
(CRRA from the utility parameters), so unlike DC-EGM it does not carry
`inverse_marginal_utility`; a new `build_bqsegm_functions` supplies just the
budget pair.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

The BQSEGM continuation integrates the child's stochastic next-states over their
joint node mesh; reading it in one pass scales the peak intermediate with the
full ride-along x node x child-grid product, which on the M1 slice (aime=38 fixed
PIA-bend grid x many ride-along axes) is enormous. Expose
n_bqsegm_stochastic_node_batch_size on GridConfig and pass it into the solver, so
a memory-rich device reads the whole mesh in one pass (0, default) while a tighter
budget loops it in blocks. Resolves the M1 solve OOM together with the upstream
pylcm splay threading.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>