Document the dashboards, alerts and local stack

[sourcehawk]

Document the dashboards, alerts and local stack

Problem

The dashboards, alert rules and render pipeline are only useful if consumers can find them, render them for their operator, understand what each alert means and how to tune it, and know to align the recorder's controller name with controller-runtime's. None of that is documented yet.

Approach

• New docs/observability.md: what ships (per-operator vs shared rule files, templated dashboard uids), render commands and variables, the namespace label, matching metrics.NewRecorder's controller name to the controller-runtime controller name, every alert with its threshold and tuning notes, both dashboards and the stale-series join, and how to run the local stack. Text only; screenshots are a manual follow-up.
• Add the page to mkdocs.yml (Guides, next to Testing), docs/index.md, the README documentation table, the reference lists and documentation table in .ai/base.md (regenerated instructions), and the plugin sync so the building-components skill references carry it and its description routes observability questions to it.
• docs/component.md Metrics section links to the new page and its controller-name example aligns with controller-runtime naming; the pkg/metrics GoDoc states the same rule; the e2e suites' recorder names follow it.

Verification

• make lint-md and make docs-build pass; the page appears in the site navigation.
• make sync-plugin and make ai-instructions leave the working tree clean after the commits.
• Every metric name, label, make target, variable, uid and alert name in the page exists in the source.

Context

Sub-issue of #183.

[sourcehawk]

Recording one decision made during implementation (PR #191) that goes beyond what this issue stated:

Before: the issue scoped the work to documentation, the docs site navigation, the AI instruction references, the plugin sync, the docs/component.md link and a README mention.

Now: documenting that the controller name passed to metrics.NewRecorder must equal the controller-runtime controller name made the repository's own e2e suites non-compliant ("e2e-component", "e2e-primitives"), so they now pass clustertestapp and testapp, with the primitives suite building one recorder per controller over a shared gauge and collectors. The pkg/metrics GoDoc carries the same rule. Screenshots were left out on purpose; the page is text only.

Why: first-party code that contradicts a rule the docs and GoDoc state is what readers copy. Label strings only; no test behaviour changed.

Implemented in 97a4924 and 80384b5.