docs: onboard AdGuard Home to Ansible; retire check-mx2; migrate plan to Linear

- Add dns.windy.lan to Ansible inventory (adguardhome group/profile) with a
  read-only healthcheck template, systemd timer, and on-demand report parity
  with the other active hosts; verified green on the host.
- Add synapse.chans.xyz to the AGENTS.md active-host quick map.
- Remove plans/; migrate decisions/verification to a Linear vps project doc and
  file the remaining gaps as W1N-46..49 with blocking edges.
- Retire scripts/check-mx2.sh; point mailcow health/update runbooks and the
  mx2 host file at the Ansible health report.
- Trim us2 stub software to verified running services; note dormant dirs.
- Normalize repo docs to English; drop the non-existent CONTEXT.md/ADR claim
  and remove docs/agents/domain.md.

docs/agents/issue-tracker.md

@@ -0,0 +1,47 @@
+# Issue tracker: Linear
+
+Issues and PRDs for this repo are tracked in Linear, driven entirely through the
+Linear MCP configured in the current runtime. VPS operation records use the
+Linear **`vps`** project (team `W1ndy`).
+
+## Conventions
+
+- **Create**: `linear_save_issue` (requires `title` + `team`); description as
+  real-newline Markdown.
+- **Read**: `linear_get_issue <identifier>` (e.g. LIN-123), optionally with
+  `includeRelations`.
+- **List**: `linear_list_issues`, filtered by `query` / `state` / `assignee` /
+  `team` / `project`.
+- **Comment**: `linear_save_comment` (pass `issueId` + `body`).
+- **Labels**: `linear_save_issue` `labels` field (replaces the whole label set).
+- **Status**: `linear_save_issue` `state` field (type / name / ID).
+
+Resolve team, project, and cycle names through the Linear MCP rather than
+hard-coding them.
+
+## Cross-issue constraint baseline
+
+The `plans/` directory is retired (removed 2026-08-06). Plans and baselines now
+live in the vps project document "VPS 运维重构：已确认决策与验收标准". Open work
+items are tracked as individual issues with dependencies expressed via
+`blockedBy` / `blocks`. Read that document before adding new tasks.
+
+## When a skill says "publish to the issue tracker"
+
+Create a Linear issue with `linear_save_issue` (`project: vps`).
+
+## When a skill says "fetch the relevant ticket"
+
+Use `linear_get_issue <identifier>`.
+
+## Wayfinding operations
+
+- **Map**: one issue as the map; child tickets link via `parentId`.
+- **Child ticket**: `linear_save_issue` with `parentId` set to the map; labels
+  `wayfinder:<type>` (research / prototype / grilling / task).
+- **Blocking**: `linear_save_issue` `blockedBy` / `blocks` (append-only).
+- **Frontier query**: list the map's open children, excluding those blocked or
+  already assigned; take the first in map order.
+- **Claim**: `linear_save_issue` `assignee: me`.
+- **Resolve**: `linear_save_comment` the answer → update `state` → append a
+  pointer under the map's decisions-so-far.