Reposition Marketplace description around runtime data and MCP

[evlawler]

Rewrites description.md, the source of the JetBrains Marketplace listing, to the new positioning: recorded runtime behavior serving both interactive diagrams (for people) and MCP query tools (for AI coding agents).

Rendered preview: description.md on this branch

What changed

• Keeps the "Runtime-aware AI starts here" opening; adds the "Why developers use it", "Works with any AI coding agent via MCP", and "Ways to use AppMap with your AI" sections (usage patterns, behavioral code scanners, OpenAPI generation) plus "The cost, measured" (June 2026 controlled-study results); promotes the visual identity into its own "See what your code actually does" section; removes retired assistant branding and the command-modes catalog (docs remain the home for those commands); replaces the pricing block with the individual-developer scope statement and a pricing page link. No em-dashes in user-facing copy.
• Interop name-checks are reduced to "any MCP-capable agent" phrasing in this listing, per the rewrite doc; the VS Code listing keeps the agent names where they carry search weight.
• The plugin display name is unchanged, and <change-notes> is untouched — the changelog entry is gated on release timing and the title rename is a separate decision.
• The listing's screenshots of the retired chat interface were dropped with their sections. A new capture of an MCP agent calling get_call_tree is assigned separately and lands in a follow-up PR; this PR ships text-first.

Notes on mechanism and risk

• No plugin.xml/CDATA editing was needed: the Gradle build renders description.md to HTML at build time (build.gradle.kts patchPluginXml), so the malformed-CDATA risk called out in the rewrite doc does not apply. The Verify Plugin CI job (which exercises that rendering) passed on the initial copy commit.
• The stale "2023.1 and newer" requirement is gone with the old copy (current builds target 2025.1+ / sinceBuild 251).
• Bundled-CLI verification passed: appmap query mcp shipped in @appland/appmap v3.200.0, which the release-manifests manifest currently serves; the plugin downloads the CLI from that manifest, so MCP is already available to existing installs.

CI status

Per team guidance, CI is not required for extension doc-only changes. All test jobs and Verify Plugin passed on the substantive copy; later commits are wording-only.

Before merging

• Confirm the docs URLs are live: /docs/reference/appmap-mcp.html, /docs/reference/jetbrains.html, and /docs/get-started-with-appmap/making-appmap-data.html.
• This listing and the VS Code listing (Reposition Marketplace listing around runtime data and MCP vscode-appland#1113) must be updated in tandem going forward.

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