feat: add anonymous telemetry tracking

[schnie]

Summary

• Add Segment-based telemetry to track CLI usage anonymously
• Users can opt-out via astro telemetry disable or ASTRO_TELEMETRY_DISABLED=1 environment variable
• Fire-and-forget pattern using detached subprocess ensures no impact on CLI responsiveness

Data Collected

• Command path (e.g., "deploy", "dev start") - NOT arguments/values
• CLI version
• OS and architecture
• Go version
• Invocation context (agent/CI/interactive)
• Anonymous user ID (UUID stored in config)

New Commands

• astro telemetry status - Show current telemetry status
• astro telemetry enable - Enable telemetry
• astro telemetry disable - Disable telemetry

Agent/CI Detection

Detects environments like Claude Code, Cursor, Aider, GitHub Actions, GitLab CI, Jenkins, CircleCI.

Test plan

• astro telemetry status shows enabled/disabled state
• astro telemetry disable disables telemetry
• astro telemetry enable re-enables telemetry
• ASTRO_TELEMETRY_DISABLED=1 environment variable overrides config
• Version command completes quickly (~0.08s) demonstrating fire-and-forget works
• All existing tests pass
• New telemetry tests pass

🤖 Generated with Claude Code

[coveralls-official]

Pull Request Test Coverage Report for Build 55a53c96-6e1c-463c-b2bf-3f94080c6774

Details

• 105 of 236 (44.49%) changed or added relevant lines in 5 files are covered.
• 127 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.04%) to 33.191%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/telemetry_send.go	8	13	61.54%
cmd/telemetry.go	61	71	85.92%
pkg/telemetry/send.go	0	45	0.0%
pkg/telemetry/telemetry.go	33	104	31.73%

Files with Coverage Reduction	New Missed Lines	%
cmd/cloud/deploy.go	10	88.89%
cloud/deploy/deploy.go	117	79.79%

Totals
Change from base Build e7f3543a-ee47-45c6-b0ae-d1b47b618aa7:	0.04%
Covered Lines:	20969
Relevant Lines:	63177

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💛 - Coveralls