feat(row6): a proposal whose approach declared no requirement is unsupported

Stress round 6 validated three falsification arms, and every validated
approach rested only on run-level declarations nobody can attribute to one
approach. declare_requirement now takes a required approach_id (a mandate
id or own-proposal; an unknown id is refused naming the valid ones), and a
ValidatedProposal whose approach has neither a mandate requirement nor a
declaration under its own id becomes validator.Unsupported - a Rejection
subclass carrying the validator's own ruling, reported as `unsupported` in
coverage, the outcome artefact, the settlement and the judge, and never
counted or summed. The rule is active whenever the debate held the
declaration tool, the micro base included; the road and pre-pass paths are
untouched. Declaration quality is not judged, so the rule can be satisfied
by declaring any document the run read.

The v1 gate's row 6 probes pass; its artefact half reads IKKE MÅLT because
stress round 6 predates approach-addressed declarations, and IKKE MÅLT is
never green - it fails the exit code.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/portfolio_optimiser/hosting.py

@@ -249,7 +249,7 @@ def _budget_payload(exc: BudgetExceeded) -> dict[str, Any]:
     """The exhausted-budget body: the ledger's own triple, plus the human line for the log.
 
     The ``budget_exhausted`` key's PRESENCE is the discriminator — it is not folded into
-    ``outcome_type`` (whose values, ``validated``/``rejected``, mean "the run concluded and
+    ``outcome_type`` (whose values, ``validated``/``rejected``/``unsupported``, mean "the run concluded and
     here is the verdict") for the same reason ``BudgetStop`` was given its own field instead of
     widening ``stop_reason``. Nor could it be: ``outcome_payload`` is the ONE copy of that fork
     and takes a ``ValidatedProposal | Rejection``, neither of which an exhausted run has."""