Prepare stable Teams CLI release

[heyitsaamir]

Summary

• move CLI versioning/package metadata to stable v3
• update CLI docs, README install snippets, and teams-dev skill guidance for stable installs
• refresh RELEASE.md with stable, preview bridge, and npm tag steps

This is stacked on #2841 so the stable release also keeps self-update on npm latest.

Validation

• npm -w @microsoft/teams.cli test -- self-update.test.ts update-info.test.ts
• npm -w @microsoft/teams.cli run build
• npm -w teams-md run build

[heyitsaamir]

This change is part of the following stack:

• Prepare stable Teams CLI release #2842 ◀

_{Change managed by git-spice.}

[Copilot]

Pull request overview

Prepares the Teams Developer CLI for stable v3 by removing preview install guidance, updating release/version metadata, and aligning agent skill docs with stable CLI expectations.

Changes:

• Switch CLI package/version metadata from prerelease to stable v3.
• Update README and docs install snippets to use npm latest.
• Refresh release/skill guidance for stable and preview bridge workflows.

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
version.json	Sets stable 3.0.{height} versioning.
packages/cli/package.json	Updates CLI package version to 3.0.0.
package-lock.json	Syncs CLI workspace package version.
README.md	Updates root install snippet to stable package.
packages/cli/README.md	Updates install snippet and table formatting.
RELEASE.md	Documents stable release, preview, bridge, and publishing steps.
teams.md/docs/cli/index.md	Removes preview warning.
teams.md/docs/cli/getting-started/installation.md	Updates CLI install command.
teams.md/docs/main/get-started/quickstart-register.md	Updates stable install command and formatting.
teams.md/docs/main/developer-tools/agent-skills.md	Updates skill requirements and formatting.
teams.md/src/pages/templates/getting-started/quickstart.mdx	Updates template install command.
teams.md/src/pages/templates/getting-started/running-in-teams/README.mdx	Updates prerequisite install command.
plugins/teams-sdk/skills/teams-dev/SKILL.md	Updates required CLI version and markdown formatting.
plugins/teams-sdk/skills/teams-dev/references/guide-create-bot-infra.md	Updates expected CLI version and install command.
plugins/teams-sdk/skills/teams-dev/references/guide-create-bot-app.md	Updates expected CLI version and formatting.