Fix [undefined](undefined) output for optional docs/link fields in llms-full.txt

[Copilot]

docs and link are optional in SoftwareSchemaObject, but the /llms-full.txt endpoint unconditionally rendered them as markdown links, producing [undefined](undefined) for entries that omit these fields (e.g. bioemu.yaml).

Changes

• src/pages/llms-full.txt.ts: Guard the - **Docs:** and - **Link:** bullet points behind existence checks so they are only emitted when the values are present.

// Before
markdownContent += `- **Docs:** [${item.data.docs}](${item.data.docs})\n`;
markdownContent += `- **Link:** [${item.data.link}](${item.data.link})\n`;

// After
if (item.data.docs) {
  markdownContent += `- **Docs:** [${item.data.docs}](${item.data.docs})\n`;
}
if (item.data.link) {
  markdownContent += `- **Link:** [${item.data.link}](${item.data.link})\n`;
}

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