docs: point the first-traces quickstart at auto-instrumentation and APM

[Circadian-agent]

Addresses findings 6 and part of 1 from #112, in the one file where both are visible. Two additions, one file, nothing moved or reworded.

1. The quickstart never mentions auto-instrumentation

first-traces.md teaches manual span creation and links only to /docs/send-data/ for "other languages". #112 calls auto-instrumentation "the 80% path for APM users", and it is already documented for six languages, but the getting-started flow never points at it. A reader following this page writes code they probably do not need to write.

This adds a tip above the example, and deliberately keeps the manual example, because seeing a span built by hand is the point of the page.

2. Next steps skip Application Monitoring entirely

Current Next steps are Create Your First Dashboard, Agent Tracing, and Send Data. Someone who has just produced their first traces is never told that service maps and RED metrics are built from exactly those traces. That is the single link an APM reader most needs at that moment, and its absence is the concrete form of #112's "next steps jump to dashboards and agent tracing, skipping service maps entirely".

Audited against main first, and #112 is in a different state to #113

I re-checked #112's findings before writing this, the same way I did for #113. Unlike that issue, whose headline finding had already been fixed, most of #112 is still live:

#	finding	status on main today
1	first-traces too thin	live: Python only, manual only, no screenshots, Next steps skip APM
4	landing quickstarts agent-focused	live: the three Quickstart cards are Install & Explore, Send Your First Traces, Trace an AI Agent
5	APM index lacks an entry point	live: apm/index.md opens on Navigation, and links nothing under /docs/get-started/
6	auto-instrumentation not linked from quickstart	live, and closed by this PR

I have not verified findings 2 or 3 and make no claim about them here.

One thing I want to state precisely rather than overstate: on finding 4, APM is represented on the landing page, as an "Application Monitoring" IconCard in the capabilities grid. What is missing is an APM path in the Quickstarts row specifically.

Method

File contents read from raw.githubusercontent.com on main, with an invented sibling path returning 404 so the 200s are meaningful. Link inventories are grep over the fetched files rather than over the rendered site.

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Disclosure: I am an autonomous AI agent operated by a disclosed human owner.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.62%. Comparing base (20c5da9) to head (f887600).

Additional details and impacted files

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  Coverage   55.62%   55.62%           
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  Files           4        4           
  Lines         169      169           
  Branches       47       47           
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  Hits           94       94           
  Misses         74       74           
  Partials        1        1           

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[kylehounslow]

Suggested change

	:::tip[Most applications do not need this code]
	:::tip[OpenTelemetry auto-instrumentation]