Stack the azure.ai.agents Next: guidance block with command highlighting

[therealjohn]

Fixes #8730

What

Restyles the Next: guidance block rendered by the azure.ai.agents extension after a successful azd ai agent deploy (and in show / init / doctor).

Before -- dense, right-aligned rows:

Next:  azd ai agent show <name>                  -- verify it's running
       see <path>/README.md                      -- find the sample-specific payload
       azd ai agent invoke <name> '<payload>'    -- test with the sample-specific payload

After -- stacked layout:

Next:
  azd ai agent show <name>
  verify it's running

  see <path>/README.md
  find the sample-specific payload

  azd ai agent invoke <name> '<payload>'
  test with the sample-specific payload

• Next: header on its own line; each suggestion is a command line over its description line, indented, with a blank line between suggestions.
• Runnable azd commands are highlighted; see ... / edit agent.yaml: ... pointers stay plain.
• Applies to all Next: blocks (deploy note plus the show / init / doctor flows).

Changes

• internal/cmd/nextstep/format.go: stacked renderer plus a highlightCommand helper; FormatNextForNote emits a leading blank line and drops the old 4-space continuation pre-indent. Sorting / truncation / trailing-reservation semantics are unchanged.
• internal/project/service_target_agent.go: append the Next: block with a single newline since the block now carries its own leading newline.
• internal/cmd/nextstep/format_test.go: updated layout goldens, TestMain color suppression, and a highlight-routing test.

Validation

• go build ./... and go test ./... pass for the extension.
• golangci-lint run reports 0 issues; cspell clean; copyright headers present.
• No go.mod / go.sum changes.

[Copilot]

Pull request overview

Updates the azure.ai.agents extension’s Next: guidance rendering to a more readable stacked layout and adds command highlighting for runnable azd ... suggestions, aligning the behavior across deploy notes and the show / init / doctor flows.

Changes:

• Reworked Next: formatting to render a header line followed by command/description pairs with blank separators.
• Added highlightCommand so runnable azd ... commands are highlighted while non-command pointers remain plain.
• Updated deploy-note concatenation and refreshed formatter goldens + added a highlight-routing test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
cli/azd/extensions/azure.ai.agents/internal/project/service_target_agent.go	Adjusts deploy-note concatenation to account for FormatNextForNote now including a leading newline.
cli/azd/extensions/azure.ai.agents/internal/cmd/nextstep/format.go	Implements stacked Next: renderer and command highlighting via output.WithHighLightFormat.
cli/azd/extensions/azure.ai.agents/internal/cmd/nextstep/format_test.go	Updates golden expectations, suppresses color globally for determinism, and adds highlight-selection coverage.