Remove technical parameter values from .nhd files (#217)

[zaucker]

Closes #217.

Technical parameter values are now sourced exclusively from technical.cfg. The redundant value = X lines in the *** technical *** sections of the .nhd model files were stale and have been removed (1069 lines across v6.5.2 + v7.0.0).

Changes

To make the cfg the single source of truth:

• Environment now carries one technical hash (the cfg values); the old .nhd fallback (technical-override // technical) is gone. A lookup of a parameter with no value now dies loudly, naming the parameter and module, instead of silently returning an undefined value. Environment gained a taxonomy attribute for that message.
• Model::Technical TWEAK only coerces value when one is present, so a parameter declaration may legitimately have no value.
• The 18 v7.0.0 parameters that were only defined in .nhd are moved into share/Models/version7.0.0/technical.cfg (v6.5.2 had none).
• All value = lines stripped from the .nhd files (declarations — name/units/description — are kept).

Test fixtures that relied on the removed fallback now ship a technical.cfg and load it, mirroring production. Adds t/technical-missing.rakutest covering the die guard.

Verification

• Full unit suite green: 547 tests (544 baseline + 3 new).
• Model outputs proven byte-identical to main for Base + Kantonal_LU on both versions (diffed a numeric dump of ~5660 output values from this branch vs a pristine main worktree).

Note for reviewers

Output-equality and die-coverage were verified for Base + Kantonal_LU only. The strip removes values for all variants, so an .nhd-only parameter live only in some other variant would now die. The known Single_old ones (er_App_cattle_liquid / er_App_pigs_liquid) are among the 18 moved, but a full all-variant scan was not performed.

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