Fix MapSet assign summary updates

[dl-alexandre]

Summary

• Carry the full updated struct through struct diffs so display nodes can refresh value-dependent collapsed content.
• Refresh struct display content while preserving existing child diffs and expanded state.
• Add a regression test for a MapSet assign whose collapsed summary changes after a diff update.

Fixes #986

Validation

• mix format --check-formatted lib/live_debugger/app/utils/term_differ.ex lib/live_debugger/app/utils/term_parser.ex test/app/utils/term_differ_test.exs test/app/utils/term_parser_test.exs
• mix test test/app/utils/term_differ_test.exs test/app/utils/term_parser_test.exs test/app/debugger/node_state/queries_test.exs test/app/debugger/node_state/web/components_test.exs
• mix test

[Copilot]

Pull request overview

Fixes a bug where collapsed display of a struct (e.g., MapSet) was not refreshed after a diff update, so users saw the original inspect output even after the value changed. The fix carries the full updated/old struct in the :struct diff and uses it to regenerate the struct's collapsed content while preserving children diffs and expansion state.

Changes:

• TermDiffer.diff/2 for structs now populates :ins/:del with the new and old struct under the primitive_key.
• TermParser.update_by_diff!/3 for :struct now refreshes the node's content/kind/key/expanded markers from the new struct via a new refresh_struct_content/3 helper, before applying child diffs.
• Adds tests covering the new diff shape and the collapsed-content refresh (including a MapSet regression case).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
lib/live_debugger/app/utils/term_differ.ex	Includes full old/new struct in :struct diff via ins/del.
lib/live_debugger/app/utils/term_parser.ex	Regenerates struct display content from updated struct while preserving children/state.
test/app/utils/term_differ_test.exs	Updates struct diff expectation to include ins/del.
test/app/utils/term_parser_test.exs	Adds regression test for MapSet collapsed content update.

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[dl-alexandre]

Thanks for the review @GuzekAlan — both points addressed in 4ca82c9:

• term_differ.ex — dropped del from the :struct diff. TermParser.refresh_struct_content/3 only reads ins, so carrying the old struct was unused memory. Kept the :struct shape minimal (ins + diff).
• term_parser.ex — primitive_key is now a @primitive_key module attribute instead of a per-call TermDiffer.primitive_key/0.
• Updated the term_differ_test.exs struct-diff expectation to match.

Compiles clean with --warnings-as-errors.

[dl-alexandre]

Addressed the latest review comments:

• Refactored refresh_struct_content/3 to use direct pattern matching on the %Diff{ins: %{@primitive_key => struct}} clause (plus a catch-all), eliminating the nested case Map.fetch/2.

• Extracted struct_summary_node/1 which builds a TermNode containing only the collapsed content/expanded_before/expanded_after/kind (with empty children) so that summary refreshes for structs like MapSet no longer unnecessarily recalculate child nodes via to_key_value_children/1.

• Extracted key_prefix_and_separator/1 to share the key-label logic and avoid duplication.

• mix format, targeted tests (term_*_test.exs, node_state tests), and --warnings-as-errors all pass.

Ready for re-review / merge. This keeps the child diff/expansion state intact while fixing the collapsed summary for changing MapSet (and other custom-Inspect structs) assigns.