chore: extract agctl module and switch to Task

[vinodvx]

Description

Splits the agctl CLI into its own Go module and migrates all build tooling from Make to [Task].

• Module split: cmd/ is now a separate module (cmd/go.mod, replace => ../) so CLI-only deps stay out of the SDK library's dependency graph. SDK and agctl are two independent builds.
• Rename: agentctl → agctl (binary, agent name, default log file agctl.log, docs).
• Make → Task: dev commands moved to the root Taskfile.yml; cmd/Taskfile.yml for the CLI (included as task cmd:*). task check runs all local gates. Makefile deleted.
• CI/Release: SDK job renamed ci → sdk; added a dedicated agctl CI job; Go module caching enabled; GoReleaser builds the cmd module (dir: ./cmd) as agctl.
• Docs: make → task throughout; Task added as a prerequisite.
• Versioning: local builds report dev; release binaries are stamped with the git tag by GoReleaser.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactor / chore

Related issues

Closes #47

Checklist

• I have run task check
• I have run task examples:all
• I have run task tidy if I added or removed dependencies
• Commit messages follow conventional commits (e.g. feat:, fix:, docs:)
• I have added/updated tests for my changes
• Documentation is updated if needed

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Project	Status	Preview	Updated (UTC)
agent-sdk-go	🟢 Ready	View Preview	Jul 19, 2026, 6:17 AM

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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