docs(guides): the migration guide #291 owed, and the index row #302 never got

[Harol-Reina]

ADR-0028 obliges a minor that carries a breaking change to ship a migration guide. [Unreleased]
holds six BREAKING entries and #291's two had none — the last documentation blocker on the
2.6.0 cut.

The guide

Both halves of #291 move something a consumer can observe, and neither changes a signature, so
nothing stops compiling. That is exactly the case a migration guide is for.

AriClient.State after a failed first connect

How the attempt ended	State before	State now
Refused upgrade (401, 503), nothing listening, name does not resolve	Connecting	Faulted
The caller cancelled the token it passed	Connecting	Disconnected

What the guide tells a consumer to delete: a poll or timeout waiting for State to leave
Connecting. It never left before; it leaves immediately now.

What it warns about:

• This amends what 2.5.3 told consumers. That release's entry pointed them at State or the
  health check, and named Connecting as what a 401 leaves behind. The throw is still exactly
  that; the state it named is not.
• AriHealthCheck keeps its status and moves its message. Connecting, Faulted and
  Disconnected all fall to the Unhealthy arm, so only the interpolated string changes — which
  matters to anyone asserting on it.
• The exception is unchanged — same type, message and stack; the state is written in a finally
  that catches nothing and runs before the exception is observable, so a caller's own catch already
  reads the terminal value.

AriOutboundListener surviving an accept failure

The old loop ended silently and for good on one transient accept failure, while IsRunning still
reported true over a socket still in LISTEN. A watchdog that restarted the listener could not
work — StartAsync refused while the flag was set. That watchdog can go, and a persistent failure is
now noisy where it used to be invisible: one Error line per failed accept, at most twelve a minute
once the backoff reaches its 5 s cap.

Also here

audiosocket-wire-format-migration.md has existed since #302 and was never listed in
docs/guides/README.md. Its row is added, so all three migration guides are now reachable from the
index — found while adding the row for the new one.

The registry row this earns

The guide restates the accept backoff bounds and their per-minute consequence. Those are quantitative
figures in a document inside the claim registry's scope, so the change carries its row (ADR-0042 D1),
classified GAP with the note that the bounds are internal constants and the per-minute figure is
arithmetic over them.

Not written, and why

#284 and #286 are also Fixed — BREAKING and get no guide: neither leaves a consumer anything to
do. A guide exists for a break that requires action, and manufacturing one for a break that requires
none makes the next reader trust the set less.

Verification

• Tests/Verbara.Sdk.OpenTelemetry.Tests — 31 passed (the claim-guard suites)
• Tests/Verbara.Sdk.Governance.Tests — 129 passed
• openspec validate --all --strict — 15 passed, 0 failed

🤖 Generated with Claude Code