Resolve link targets inside typed dynamic entries during from_dict

[elinscott]

Problem

A graph whose typed dynamic output namespace entries are populated key-by-key from leaf sockets cannot be reconstructed from its dict form — which build(), run() and the daemon all rely on:

class Entry(TypedDict):
    value: int
    tag: int

@task.graph
def Produce(x: int) -> Entry:
    return Entry(value=compute(x).result, tag=compute(-x).result)

@task.graph
def Parent(items: dict) -> Annotated[dict, dynamic(Entry)]:
    entries = {}
    for label, x in items.items():
        produced = Produce(x)
        # per-key socket picking into the dynamic entry
        entries[label] = Entry(value=produced.value, tag=produced.tag)
    return entries

Parent.build(items={"a": 1, "b": 2})
# ValueError: Missing socket 'a.value' in graph_outputs.inputs and
# parent namespace is not dynamic.

The per-key links create the entry namespaces (a, b) in the live graph, but reconstruction refuses to re-create their children because the typed entry itself is not marked dynamic.

Changes

• Extract the dotted-path input-socket resolution from links_from_dict into a Graph._resolve_or_create_input_socket helper (mechanical, first commit)
• Walking the dotted target path materializes the entry namespace from the dynamic parent's item spec, which already creates the entry's children per that spec; the resolver then returns an existing leaf before checking dynamism, instead of refusing to create it because the typed entry itself is not dynamic (second commit)

Testing

• New round-trip regression test in test_graph.py: a typed dynamic output namespace populated by per-key leaf links survives to_dict → from_dict
• Unit tests covering the resolver's error branches (missing sockets under non-dynamic namespaces, descent through a leaf), which the extraction had moved out of inline code untested
• Full suite passes with no changes to existing tests

[codecov]

Codecov Report

❌ Patch coverage is 92.18750% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.82%. Comparing base (8d85e61) to head (ffde95c).

Files with missing lines	Patch %	Lines
tests/test_graph.py	91.17%	3 Missing ⚠️
src/node_graph/graph.py	93.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #166      +/-   ##
==========================================
+ Coverage   89.68%   89.82%   +0.14%     
==========================================
  Files          81       81              
  Lines        8984     9020      +36     
==========================================
+ Hits         8057     8102      +45     
+ Misses        927      918       -9     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.