Expand & cross-link the datumctl CLI documentation

[scotwells]

Expands the datumctl (CLI) documentation section from a thin set of pages into a coherent, well-linked guide, and makes information flow between every doc with descriptive link text.

New guides

• Quickstart — install → log in → set context → first command.
• Contexts & scoping — the organization/project model, datumctl ctx, and the --organization/--project flags (the Fix writing style and tone inconsistencies #1 source of "why do I see nothing?" confusion).
• Output formats & scripting — -o formats, structured --error-format, and automation/agent patterns.
• Discovering resources & schemas — api-resources, api-versions, and explain.
• Interactive console — datumctl console panes, navigation, dashboards, and in-console login.
• AI assistant & MCP — datumctl ai and the datumctl mcp server (cross-linked with the Agents-tab MCP page).
• Using datumctl with kubectl — opt-in auth update-kubeconfig/whoami/can-i for kubectl users only.

Section-wide weave

• Restructured the CLI tab into groups: Getting started · Core concepts · Interactive & AI · Plugins · Reference & interop.
• Un-orphanedworking-with-resources and console (both were missing from the nav) and de-duplicated overlapping content down to single canonical homes.
• Added descriptive cross-links (no bare URLs or "click here") throughout the new and existing docs so readers move naturally between related tasks.

Every command, flag, and keybinding was verified against the datumctl source. docs.json validated.

Stacked on docs/datumctl-plugins (PR #37) so the plugin cross-links resolve — retarget to main once that merges.

🤖 Generated with Claude Code

[scotwells]

Folded into #37 so the CLI guides and plugin docs share one preview environment. All commits are now on docs/datumctl-plugins.