chore: release 2.18.0

[github-actions]

🤖 I have created a release beep boop

2.18.0 (2026-01-13)

Features

• aclocal,automake: support versioned 1.17 executables (94bbb3a)
• pnpm: add 3rd party fallback completion loader (44804ae)
• pydoc: support versioned 3.13..15 executables (bd60b26)
• python,pyvenv: support versioned 3.14 and .15 executables (72a2e47)
• release-plz: add 3rd party fallback completion loader (c3c4066)
• ssh-keygen: -M arg completion (b13bf99)
• ssh-keygen: -Z argument completion (c763d52)
• ssh-keygen: more option arg completions (1303f8a)
• ssh-keygen: update -t arg completions (4269a90)
• ssh-keygen: update -Y arg completions (a73bcaf)
• sudo-rs,sudo.ws: alias to sudo (084cc68)
• sudo: more option argument (non-)completions (379ec2d)
• sudo: more option argument (non-)completions (216135e)
• tmux: complete src/target session arguments (18b6da4)
• tmux: complete target-session arguments (ced59c3)
• waydroid: add 3rd party fallback completion loader (acc800f)

Bug Fixes

• _comp_compgen: clear the variable when no completions are generated (c07bd66)
• _comp_complete_service: fix init-script-action parsing (#1499) (91e075a)
• cd: Complete from . on empty CDPATH entry (#1527) (6f1eba6)
• cd: fix cdable_vars overwritten by another generator (225b8ab)
• cd: fix cdable_vars overwritten by another generator (24bd420)
• cd: work around bash-4.2 nounset (45d1c93)

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This PR was generated with Release Please. See documentation.

[scop]

Sigh, googleapis/release-please#2613

[yedayak]

Before merging this, I think there should be a note at the beginning mentioning the reordering of the completion directories, since it will probably affect distributions.