fix: detect parameter reordering as a breaking change in diff.rs

[CodedTricks]

Summary

crates/lumenqraph-core/src/diff.rs computes interface diffs by rendering function signatures as strings and comparing them. When a function's parameters are reordered (e.g. transfer(from, to, amount) → transfer(amount, from, to)), the string changed and the diff did mark it breaking — but only via the generic changed bucket. The summary line said "changed function transfer: …" with no indication that only the order changed.

Since Soroban encoding is positional, a reorder breaks every caller that passes arguments by position. It deserves its own reordered change type so operators and webhook subscribers can immediately tell what kind of breaking change occurred.

What was implemented

• ReorderedItem struct — mirrors ChangedItem (name, from, to)
• SectionDiff.reordered — new Vec<ReorderedItem> field
• is_empty / has_breaking — updated to include reordered
• function_sigs() — now returns (BTreeMap<name, sig>, BTreeMap<name, params>) so the diff logic has the ordered parameter list per function
• diff_section_with_params() — new helper that, when two signatures differ, checks whether the param set is the same but the order differs (is_param_reorder helper); if so, pushes to reordered instead of changed
• build_summary() — emits "reordered function <name>: <from> became <to>" lines
• crates/lumenqraph-core/Cargo.toml — adds missing url and tokio/net dependencies required by url_validation.rs (pre-existing omission that prevented the crate from building with the stable toolchain)

Tests

Two new tests added:

• reordered_parameters_are_breaking_and_flagged_as_reordered — verifies the reordered bucket is used, changed is empty, breaking is true, and the summary line starts with "reordered function transfer"
• renamed_parameter_is_changed_not_reordered — regression guard ensuring a rename still goes to changed, not reordered

All 21 diff tests pass.

Closes Lumen-Scribe#256