feat: add local Connection service authoring

[Hui Miao (huimiu)]

Fixes #10478

Summary

Complete layer 4/4 of the Connection authoring stack. This PR depends on #10472 and adds azd ai connection add to author Connection services in an existing local project without reading environment values, resolving secrets, or creating remote resources.

Closes #10351.

Changes

• Add contained definition-file references to the actual nearest azure.yaml or azure.yml, with deterministic add/update/no-op results and explicit Project ownership selection or repair.
• Preserve unrelated service settings, environment entries, literal templates, explicit empty environment mappings, and large integers. Reject conflicting service names, malformed dependencies, ineffective flags, and unsupported output before mutation.
• Use the preview conditional raw service-authoring API while retaining the published azd SDK v1.34.0 dependency, and require azd >=1.36.0-beta.1. Keep prompts on stderr and JSON results on the injected writer.
• Update help snapshots, Connection schema, extension documentation, feature status, and offline scenario fixtures.

Validation: Full Connections tests and build pass; golangci-lint reports zero issues; gofmt and go fix produce no changes; scoped spelling and whitespace checks pass. Core dispatch, injected prompt-writer, beta authoring/adapter/concurrency regressions pass, including three repeated focused runs. Fifteen isolated real host/extension invocations pass for add, update, byte-identical no-op, wrong-host/name rejection, invalid output/flags, azure.yml, multiple Project selection, and empty-env/large-integer preservation. Validation used a disposable AZD_CONFIG_DIR, disabled telemetry, and unreachable HTTP(S) proxies; no Azure login or resource operations were performed.

Limitations: The cli-interactive-tester runner itself was not executed. Its nine scenario/fixture YAML files were parsed, and the equivalent offline command contracts were exercised directly. Race-detector execution is blocked because GCC is unavailable; non-race concurrency regressions pass.

Aggregate source comparison: The final stacked tree matches immutable source fae306e11bb6a9893380e63c4786026684bc07ea except for these documented non-functional/documentation improvements:

• cli/azd/.vscode/cspell.yaml: retain layer 3's expanded generated-header spelling allowance; include the source's connection_project.go allowance.
• cli/azd/pkg/azdext/extension_command.go: retain layer 2's comment wrapping.
• cli/azd/extensions/azure.ai.connections/internal/cmd/connection_project_test.go and internal/cmd/root.go: shorten/wrap comments to the requested 70-character limit and accurately label local/remote commands.
• cli/azd/extensions/azure.ai.connections/README.md: clarify optional-variable bindings and required-only reporting.

No lower-layer implementation, module, generated, or contract files are changed by this PR.

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[azure-sdk-automation]

azure.ai.connections PR build

Note

This is an unsigned development build. Install it only if you trust this PR.

Install the extension:

azd ext install "https://azuresdkartifacts.z5.web.core.windows.net/azd/extensions/pr/10473/azure-ai-connections.zip"

• Version: 1.0.0-beta.9.pr.10473.6956221
• Merge commit: 6de320c

[github-actions]

📋 Prioritization Note

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Thank you for logging this issue; our team is reviewing it. If you need urgent prioritization, tag Rick Winter (@RickWinter) and Kristen Womack (@kristenwomack) to let us know.