Fix prepare-providers-documentation skill tag detection (dotted-id + sentinel/rc tags)

[potiuk]

The prepare-providers-documentation agentic skill's Phase 2 / Incremental Phase 2 git query for the last release tag had two defects discovered during the 2026-06-02 release prep:

• Dotted provider ids use hyphens in tag names (providers-cncf-kubernetes/<ver>), but the skill built the tag pattern from the slash-converted folder path (providers-cncf/kubernetes/*) → matched no tags → empty commit lists for ~10 dotted providers.
• Sentinel + rc tags polluted "latest tag" selection: a bare --sort=-v:refname | head -n1 picks the 99.98.0/99.99.0 sentinel upper-bound tags and rc tags (git sorts 1.2.0rc1 after 1.2.0) — e.g. yielding a bogus ~600-commit "amazon" range.

Fixes both queries to derive the tag segment with tr '.' '-', exclude 99.9x sentinels and rcN, and adds a warning that breeze's Phase 1 discovery output is the authoritative commit set (the tag-based range can still diverge when a provider's latest final tag is not the last published release).

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Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Opus 4.8)

Generated-by: Claude Code (Opus 4.8) following the guidelines

[github-actions]

Backport successfully created: v3-2-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-2-test