fix(gitea-issues): list_issues does have type and milestones on v1.7.0

SKILL.md's headline Gotcha said `list_issues` "has no `type` filter", and
references/issues.md stated in bold that neither `type` nor `milestones`
exists, "despite both appearing in api-reference.md". Both parameters are
present on the deployed gitea-mcp v1.7.0 and both work: `type: "issues"`
returns only issues, `type: "pulls"` only PRs, and `milestones` filters by
name. Unfiltered, the same window returns them interleaved, so the mixing
the Gotcha describes is real — only the stated remedy was wrong.

This mattered most in gitea-workflow's no-args check-in, which lists open
issues through this skill and so reported PRs under "Open Issues" while
the skill forbade the one-parameter fix. The list flow now passes
`type: "issues"`.

references/sources.md recorded the absence as a live-verification win over
stale research docs; it now records that the earlier check was superseded
by v1.7.0, since drift runs in both directions. gitea-prs cited the same
parameter as its canonical drift example and no longer does — no
replacement example was substituted, because the obvious candidate was not
verified in this pass.

Also defaults label writes to `add_labels`: `replace_labels` clears every
label not in the array, and per-label exclusivity makes blanket replacement
destructive for a non-exclusive scope.

Verified live against gitea-mcp v1.7.0, read-only calls.

Refs #99

plugins/gitea/skills/gitea-issues/references/search.md

@@ -13,8 +13,8 @@ time (see `references/sources.md`) — confirmed to match `api-reference.md`.
 **Parameters:**
 - `query` (string, required) — the only hard-required parameter
 - `state` (string, enum `"open"` | `"closed"` | `"all"`, optional)
-- `type` (string, enum `"issues"` | `"pulls"`, optional) — **this tool has a working type filter**,
-  unlike `list_issues` (see `references/issues.md`)
+- `type` (string, enum `"issues"` | `"pulls"`, optional) — the same filter, with the same values,
+  that `list_issues` takes (see `references/issues.md`)
 - `labels` (string, optional) — comma-separated label **names** — a plain string, not the array form
   `list_issues` uses
 - `owner` (string, optional) — restrict results to one owner