(feat) Add Cursor Marketplace plugin form (#119)

* feat(cursor): add Marketplace plugin form

Ships .cursor-plugin/plugin.json + cursor/plugin-hooks.json so the repo is
installable from the Cursor Marketplace, alongside the existing
install-cursor.sh flow. The plugin form uses a relative ./scripts/cursor-on-event.sh
path (resolved from the plugin root) instead of $HOME/.local/share/...,
which let the existing bootstrap script stay unchanged.

Adds commands/dash0-configure.md to replace the installer's interactive
prompt: end users run /dash0-configure inside Cursor to write the OTLP
URL + token to ~/.cursor/dash0-agent-plugin.local.md.

release.sh now bumps .cursor-plugin/plugin.json alongside the others, and
cursor/README.md documents both install paths.

* build: resolve installer version from GitHub at runtime

install-cursor.sh no longer carries a hardcoded VERSION. It queries the
GitHub API for the latest release on each run, with DASH0_VERSION as an
override for pinning. Removes the failure mode where a release that
skipped scripts/release.sh would leave the installer pointing at the
previous tag.

release.sh and cursor/README.md updated to reflect that install-cursor.sh
is no longer part of the version-bump set.

* fix(cursor): expose configure step as a skill, not a command

Cursor's user-invocable unit is a skill (SKILL.md with name + description
frontmatter), surfaced to the agent semantically. The original commands/
path was a Claude Code shape that Cursor's plugin loader did not pick up
during local sideload testing.

Replaces commands/dash0-configure.md with skills/dash0-configure/SKILL.md
and updates the manifest accordingly. Claude Code's commands/open-session.md
and .claude-plugin/plugin.json are unchanged.

* docs: split runtime READMEs by audience

Root README is now a hub — it pitches the idea (connect coding agents to
Dash0 for deep insight into AI usage) and points at the per-runtime docs.

Claude Code docs move to .claude-plugin/README.md (unchanged content,
just relocated). New .cursor-plugin/README.md holds end-user-facing
Cursor docs: install via Marketplace or shell installer, configure via
the dash0-configure skill, verify, uninstall. cursor/README.md becomes
the developer reference (build, sideload local changes, cut releases,
capture-mode fixtures), with a pointer to the user-facing README.

Drops the stale cursor-source-handoff-brief.md — the research it
captured has been folded into the integration.

* Point consistency check to claude readme

* build: add cursor plugin-template validate script

Copied verbatim from cursor/plugin-template@main:
  scripts/validate-template.mjs

Required for Cursor Marketplace submission. The script expects a
multi-plugin .cursor-plugin/marketplace.json layout — since this repo
is a single plugin, the validator early-returns "Validation passed"
without actually checking the manifest. Present-in-repo is what the
submission process appears to need; real validation would require
either a marketplace-style restructure or a single-plugin validator.

Author: k-berger

.claude-plugin/README.md

@@ -0,0 +1,77 @@
+# Dash0 Agent Plugin — Cursor
+
+Cursor plugin that emits agent activity as OpenTelemetry spans to your Dash0 endpoint — prompts and responses, tool calls, MCP calls, and sub-agent activity, with shared trace context across each turn.
+
+## Installation
+
+Two install paths. Both end up with the same on-device layout (`cursor-on-event` binary + bootstrap script + config file + hooks registration).
+
+### Cursor Marketplace (recommended)
+
+1. Install `dash0-agent-plugin` from the Cursor Marketplace. Cursor reads `.cursor-plugin/plugin.json` and registers the hooks declared in `cursor/plugin-hooks.json`.
+2. Ask the agent to *configure Dash0* — the `dash0-configure` skill walks you through writing `~/.cursor/dash0-agent-plugin.local.md` with your OTLP URL, auth token, and optional dataset / team / agent name.
+3. Quit and relaunch Cursor (Cmd+Q on macOS) — Cursor reads `hooks.json` only at startup.
+
+The plugin ships no binary. The bootstrap script downloads `cursor-on-event-<os>-<arch>` from [GitHub Releases](https://github.com/dash0hq/dash0-agent-plugin/releases) on first hook fire and verifies the checksum.
+
+### Shell installer
+
+Non-interactive single-command install. Useful for CI, provisioning, or skipping the configure skill.
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/dash0hq/dash0-agent-plugin/main/install-cursor.sh | bash
+```
+
+Pre-supply credentials via env vars to skip the prompts:
+
+```bash
+DASH0_OTLP_URL=https://ingress.<region>.aws.dash0.com \
+DASH0_AUTH_TOKEN=<your-token> \
+DASH0_DATASET=default \
+  curl -fsSL https://raw.githubusercontent.com/dash0hq/dash0-agent-plugin/main/install-cursor.sh | bash
+```
+
+Optional env vars: `DASH0_DATASET`, `DASH0_AGENT_NAME`, `DASH0_TEAM_NAME`, `DASH0_VERSION` (pin a specific release; default: latest GitHub release).
+
+After install, **quit and relaunch Cursor.**
+
+## Configuration
+
+The config file lives at `~/.cursor/dash0-agent-plugin.local.md` (chmod 600 — it holds your token in cleartext). YAML frontmatter:
+
+```yaml
+---
+otlp_url: "https://ingress.<region>.aws.dash0.com"
+auth_token: "<your-dash0-auth-token>"
+dataset: "default"            # optional
+agent_name: "cursor"          # optional — used as service.name
+team_name: "<your-team>"      # optional — tagged as dash0.team.name on every span
+omit_io: false                # set true to redact prompts and tool input/output
+---
+```
+
+To reconfigure later, re-run the `dash0-configure` skill in Cursor, or edit the file directly. Config changes take effect on the next hook fire — no restart needed. (Restart is only needed if `hooks.json` itself changes, since Cursor reads it at startup.)
+
+## Verify
+
+Send a prompt that uses a tool. In Dash0 you should see one trace per turn with:
+
+- one `chat default` span at turn end carrying `gen_ai.usage.input_tokens`, `output_tokens`, and `cache_read.input_tokens`
+- one `execute_tool <Name>` span per tool call, with `parentSpanId` pointing at the chat span
+- the same `traceId` on every span in the turn
+
+If nothing arrives, set `debug: true` and `debug_file: /tmp/dash0-cursor-debug.log` in the config. Every emitted span is also appended there as a `[dash0:trace] {...}` line:
+
+```bash
+tail -F /tmp/dash0-cursor-debug.log
+```
+
+## Uninstall
+
+```bash
+rm -rf ~/.local/state/dash0-agent-plugin \
+       ~/.local/share/dash0-agent-plugin \
+       ~/.cursor/dash0-agent-plugin.local.md
+```
+
+If you installed via `install-cursor.sh`, also remove `~/.cursor/hooks.json`. If you installed via the Marketplace, uninstall the plugin from Cursor's plugin UI.

.cursor-plugin/README.md

@@ -0,0 +1,14 @@
+{
+  "name": "dash0-agent-plugin",
+  "version": "0.1.10",
+  "description": "OpenTelemetry observability for Cursor sessions. Captures prompts, tool calls, MCP calls, and subagent activity as OTel traces.",
+  "author": {
+    "name": "Dash0"
+  },
+  "homepage": "https://dash0.com",
+  "repository": "https://github.com/dash0hq/dash0-agent-plugin",
+  "license": "Apache-2.0",
+  "keywords": ["observability", "tracing", "opentelemetry", "dash0", "otel"],
+  "hooks": "cursor/plugin-hooks.json",
+  "skills": "./skills/"
+}

.cursor-plugin/plugin.json

@@ -305,7 +305,7 @@ jobs:
           DECLARED_KEYS=$(jq -r '.userConfig // {} | keys[]' .claude-plugin/plugin.json | sort -u)
           MISSING=""
           for key in $DECLARED_KEYS; do
-            if ! grep -qF "| \`$key\`" README.md; then
+            if ! grep -qF "| \`$key\`" .claude-plugin/README.md; then
               MISSING="$MISSING $key"
             fi
           done