fix: reconstruct namespace root of dotted {% set ns.attr %} across scopes

[jasmith-hs]

What

When eager (two-phase) execution defers a dotted namespace assignment like {% set ns.attr = value %}, also reconstruct the namespace root ns in the scope that owns it — matching the behavior that already exists for {% do ns.update(...) %}.

Why

Eager execution renders a template in a first phase and defers anything it can't yet resolve into a reconstructed template that a second phase renders with the full context. For this to stay correct, any variable a deferred region mutates has to be deferred/reconstructed in the scope where it lives, or the first phase reads a stale value and the two phases diverge.

This already worked for in-place collection mutation via {% do %}: {% do list.append(x) %} reads list to call .append, so list is tracked as a used deferred base and is deferred/reconstructed unconditionally up the context chain.

Dotted namespace assignment behaved differently. {% set ns.attr = x %} tracked ns only as a set deferred base, and set bases are deferred only when isInSameScope is true (the same macro-stack). A plain deferred {% if %} or {% for %} shares the macro stack, so that case worked. But when the assignment runs across a macro boundary — or inside a child interpreter context, which is how some host frameworks pre-render fragments — the deferral of ns never reached the scope where ns was defined. The first phase then read the namespace as unmutated, so a later {{ ns.attr }} (or {% if ns.attr %}) resolved against the wrong value and the reconstructed template dropped the mutation entirely.

Fix

When the left-hand side of a {% set %} is a dotted assignment whose root resolves to a Namespace, register that root as a used deferred word in addition to the existing set word. Mutating ns.attr inherently reads ns, so treating the root as a used base is semantically honest, and it reuses the existing, proven propagation/reconstruction path rather than widening the scope gate for all set tags. The instanceof Namespace guard leaves plain-map dotted keys ({% set someMap.field = x %}, which jinjava stores as a literal "someMap.field" key) untouched.

Tests

• EagerSetTagTest: the namespace root is registered as a used deferred word for both inline and block dotted sets; a non-namespace map root is not registered (guard); a namespace holding a non-serializable attribute value does not throw during reconstruction.
• EagerTest: end-to-end reconstruction + second-pass parity for a dotted namespace set inside a macro (the cross-scope case that regressed) and inside a {% for %} loop, each asserting the eager result matches a plain non-eager render.

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PR description authored by Claude Code.