feat(agent): add order field for configurable agent cycling order

[LCubero]

Closes #7372

Adds an optional order field (PositiveInt) to agent config so users and plugins can control Tab cycling order instead of being forced into alphabetical sort.

Currently Agent.list() sorts agents alphabetically by name (after default agent). This breaks plugins that define multiple agents with a specific intended order.

The fix adds order (positive integer, optional) to both ConfigAgent.Info and Agent.Info. Sorting becomes:

1. Default agent first (unchanged)
2. By order ascending (new)
3. By name ascending (unchanged fallback)

Changes

• packages/opencode/src/config/agent.ts: Add order to AgentSchema + KNOWN_KEYS
• packages/opencode/src/agent/agent.ts: Add order to Info schema, merge logic, and sortBy
• packages/opencode/test/agent/agent.test.ts: Add 2 tests for order field sorting

How verified

• Two new unit tests: order field sorting and mixed ordered/unordered agents
• Existing alphabetical sort test renamed and still passes
• Backward compatible: agents without order sort alphabetically as before

[github-actions]

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate PRs Found

Based on my search, I found 3 potentially related PRs:

1. PR feat(agent): add order field for configurable agent cycling order #24691 - "feat(agent): add order field for configurable agent cycling order"

   • feat(agent): add order field for configurable agent cycling order #24691

2. PR feat(agent): add order field for configurable agent cycling order #19127 - "feat(agent): add order field for configurable agent cycling order"

   • feat(agent): add order field for configurable agent cycling order #19127

3. PR feat(opencode): add order field to agent config for explicit list sorting #22343 - "feat(opencode): add order field to agent config for explicit list sorting"

   • feat(opencode): add order field to agent config for explicit list sorting #22343

Why they're related: All three PRs are implementing the same feature - adding an order field to agent configuration to control the cycling/sorting order of agents instead of relying on alphabetical sorting. This appears to be a frequently attempted feature addressing the same underlying issue.