unique-metas emits a meaningless context (the meta head string) for duplicated metas

Problem

For duplicated metas, unique-metas emits a defect whose @context is the meta head string (e.g. "version") instead of the actual duplicate meta element — the context is useless for locating the second occurrence.

Root cause

src/main/resources/org/eolang/lints/metas/unique-metas.xsl:23-26 calls eo:defect-context(.) inside <xsl:for-each select="$unique">, where the context node is the string produced by the grouping ($unique is a string sequence), not an element. Verified: the resulting context attribute is [version].

Minimal example

+package x
+architect yegor@256.com
+version 0.0.1
+version 0.0.2
+home https://github.com/objectionary
+spdx SPDX-FileCopyrightText: Copyright (c) 2026 Objectionary.com
+spdx SPDX-License-Identifier: MIT

[] > main

The defect for the duplicate +version meta carries context="[version]" rather than the serialized second meta element.

Expected behavior

eo:defect-context should be computed from the actual duplicated meta element, e.g. $metas[head=$head][2], so the context shows the offending line's content.

Related

• funcs/defect-context.xsl — the context serializer; used correctly by other lints (e.g. empty-alias).

Start with src/main/resources/org/eolang/lints/metas/unique-metas.xsl:23-26 and inspect how the $unique sequence is used inside xsl:for-each. Compare the context handling with funcs/defect-context.xsl and the empty-alias lint. Use the minimal EO example to verify that the duplicate version defect context identifies the second meta element rather than showing [version].