refactor: move optional arguments of make functions behind the ellipsis

[krlmlr]

Part of the repo-wide ellipsis migration coordinated in #2757 —
see that PR for the full rationale (CONTRIBUTING.md, Argument Order and the Ellipsis).
Based directly on main (the registry split landed via #2779); a single topic commit.

What this does

Inserts ... between the defining arguments (head) and the optional
modifiers (tail) of 23 exported make functions.
Arguments after ... become keyword-only.

• Legacy positional or abbreviated calls are recovered by the generated
  ARG_HANDLE block and emit a single lifecycle::deprecate_soft("3.0.0", …) —
  behavior is unchanged.
• No defaults change, no arguments are renamed, deprecated functions untouched.
• Registry: tools/migrations/make.R; blocks regenerated via
  Rscript tools/generate-migrations.R (idempotent, CI-checked).
• Rd usage/arguments updated mechanically (see note below).

New signatures

function	head (positional)	keyword-only tail
bipartite_graph()	types, edges	directed
chordal_ring()	n, w	directed
circulant()	n, shifts	directed
empty_graph()	n	directed
full_bipartite_graph()	n1, n2	directed, mode
full_citation_graph()	n	directed
full_graph()	n	directed, loops
full_multipartite()	n	directed, mode
make_bipartite_graph()	types, edges	directed
make_chordal_ring()	n, w	directed
make_circulant()	n, shifts	directed
make_empty_graph()	n	directed
make_full_bipartite_graph()	n1, n2	directed, mode
make_full_citation_graph()	n	directed
make_full_graph()	n	directed, loops
make_full_multipartite()	n	directed, mode
make_ring()	n	directed, mutual, circular
make_star()	n	mode, center
make_tree()	n, children	mode
realize_degseq()	out.deg, in.deg	allowed.edge.types, method
ring()	n	directed, mutual, circular
sample_tree()	n	directed, method
star()	n	mode, center

Notes for review

• The environment used to prepare this PR cannot install igraph.r2cdocs
  (GitHub API unreachable), so man/*.Rd files were updated mechanically
  (usage + ... argument item) instead of via devtools::document().
  R CMD check's usage↔formals validation passes; a follow-up
  devtools::document() run may reflow whitespace but should produce no
  semantic diff.
• Package tests that called these functions positionally were updated to
  named arguments (they are the same soft-deprecation user code will see).

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 7e520e0 is merged into main:

• ✔️as_adjacency_matrix: 761ms -> 760ms [-0.71%, +0.4%]
• ✔️as_biadjacency_matrix: 740ms -> 737ms [-0.98%, +0.15%]
• ✔️as_data_frame_both: 1.48ms -> 1.47ms [-2.61%, +1.31%]
• ✔️as_long_data_frame: 3.94ms -> 3.9ms [-3.48%, +1.82%]
• ✔️es_attr_filter: 2.67ms -> 2.68ms [-0.79%, +1.6%]
• ✔️graph_from_adjacency_matrix: 116ms -> 116ms [-0.7%, +0.78%]
• ✔️graph_from_data_frame: 3.34ms -> 3.35ms [-1.09%, +1.89%]
• ✔️vs_attr_filter: 1.53ms -> 1.52ms [-3.76%, +1.84%]
• ✔️vs_by_name: 963µs -> 966µs [-0.9%, +1.66%]
  Further explanation regarding interpretation and methodology can be found in the documentation.