ci: release.yml reports failures on develop/branch pushes

[neuromechanist]

Problem

The release.yml workflow is reporting failures on pushes, including on develop and feature branches, even though its trigger is tags-only:

on:
  push:
    tags:
      - 'v*'

gh run list --workflow release.yml shows recent runs with event=push and conclusion=failure on develop and feature branches (e.g. while merging the recent papers PRs). It is not a required PR check, so it has not blocked merges, but it pollutes CI status (PRs show as UNSTABLE) and may indicate a real misconfiguration.

Hypotheses to check

1. The failing runs are triggered by the v* tags that tag-release.yml creates; GitHub reports the run's headBranch as the branch containing the tagged commit (hence develop). The failure is then inside the release job itself (e.g. the "Get version from tag" step or release creation) - investigate which step fails and why.
2. A tag is being created/pushed in a context where the release job's assumptions don't hold (e.g. version parsing, missing permissions, or a duplicate-release conflict).

Acceptance

• Identify the failing step in release.yml and the trigger that produces these runs.
• Either fix the job so tag-triggered releases succeed, or correct the trigger/guard so it doesn't run-and-fail in non-release contexts.
• CI status on PRs/branches no longer shows spurious release.yml failures.

Notes

• Pre-existing; unrelated to the recent papers/opencite work (fix(search): paper/knowledge search returns nothing for multi-word queries #305/refactor(papers): use opencite for paper sync + declare dependency #307/feat(papers): optional live 'search most recent papers' via opencite #308/refactor(papers): use opencite for paper sync + declare dependency #309). Surfaced while watching CI on those PRs.