refactor: Rename algo to algorithm in page_rank(), feedback_arc_set() and feedback_vertex_set()

[krlmlr]

Part of #2788 (PR 1 of a stack of 6, least controversial first); implements the algo → algorithm leg of #526.

What this does

• Renames the algo argument to algorithm in page_rank(), feedback_arc_set() and feedback_vertex_set() — the three functions the Comprehensive plan: argument renames for 3.0.0 #2788 survey lists under the algo spelling. All three already carry their 3.0.0 keyword-only migration entries with algo after ..., so the rename is a pure registry change (algo = algorithm bare-symbol rename in tools/migrations/), and legacy algo = callers are recovered with the same single soft-deprecation as positional callers:

  Calling `page_rank()` with positional or abbreviated arguments was deprecated in igraph 3.0.0.
  i Detected call: page_rank(graph, algo)
  i Use instead: page_rank(graph, algorithm = )
  

• Abbreviations that could mean either spelling (a, al, alg) are rejected as ambiguous by the regenerated ARG_HANDLE guards.

• The deprecated page.rank() wrapper keeps its frozen algo formal (now documented locally with a deprecated badge, since @inheritParams page_rank no longer carries it) and forwards to algorithm.

• Tests: named uses updated, plus new coverage that the legacy name is recovered (snapshot for page_rank(algo = ), expect_deprecated for the two feedback functions).

Out of scope

method (12 algorithm-choice + 2 comparison-metric functions), implementation (2) and impl (1) are the open "algorithm family" questions in #2788 and are not touched here.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RTPj4qNv2FWui6etixZeuR

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Generated by Claude Code

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 12230f8 is merged into main:

• ✔️as_adjacency_matrix: 761ms -> 762ms [-0.87%, +1.09%]
• ✔️as_biadjacency_matrix: 769ms -> 768ms [-0.88%, +0.6%]
• ✔️as_data_frame_both: 1.89ms -> 1.88ms [-1.95%, +1.01%]
• ✔️as_long_data_frame: 4.75ms -> 4.77ms [-1.01%, +1.74%]
• ✔️es_attr_filter: 3.31ms -> 3.33ms [-0.66%, +1.89%]
• ✔️graph_from_adjacency_matrix: 120ms -> 121ms [-0.68%, +0.98%]
• ✔️graph_from_data_frame: 4.08ms -> 4.06ms [-1.88%, +0.79%]
• ❗🐌vs_attr_filter: 1.76ms -> 1.79ms [+0.2%, +2.85%]
• ✔️vs_by_name: 1.14ms -> 1.16ms [-2.05%, +4.46%]
  Further explanation regarding interpretation and methodology can be found in the documentation.