fix(gitea): correct is_draft param and soften unverified claims in gitea-releases docs

An audit against plugins/gitea/docs/research/docs/gitea/*.md found the
gitea-releases skill told callers to set create_release's draft flag
as `draft` instead of `is_draft` (the actual input param; `draft` is
only the response field name) - a call following that gotcha would
have the flag silently ignored, publishing a non-draft release.

Also corrected an overclaimed "verified against live MCP schema"
provenance note in call-signatures.md/README.md (its sources are
gitea-mcp source-code extraction, not a live tool call - now noted
alongside a narrow live ToolSearch cross-check performed this session
for 3 of the 9 tools' input params), and softened three behavioral
claims (create_release auto-creating tags, get_latest_release
excluding drafts/prereleases, delete_tag preserving a wrapping
release) that don't trace to any research doc, with a recommendation
to verify release/tag state after delete operations rather than
assume it.

plugins/gitea/skills/gitea-releases/README.md

@@ -19,6 +19,6 @@ Describe your release/tag task: list releases, get the latest release, create a
 | File | Purpose |
 |------|---------|
 | `SKILL.md` | Skill instructions for agents |
-| `references/call-signatures.md` | Verified tool parameters and response shapes for all 9 release/tag tools |
+| `references/call-signatures.md` | Tool parameters and response shapes derived from gitea-mcp source (see `references/sources.md`); input params for 3 of the 9 tools additionally live-cross-checked |
 | `references/conventions.md` | Semver/draft/prerelease practitioner conventions and pagination behavior |
 | `references/sources.md` | Research sources backing the call signatures and conventions |