[NOT-779] Remove agents from notte-cli

[leo-notte]

Summary

• remove the notte agents command group and its generated flags
• remove agent state, validation, command tests, integration coverage, and documentation
• keep session and function workflows intact

Validation

• git diff --check
• Go tooling is unavailable in this environment, so the Go test suite was not run.

[greptile-apps]

Greptile Summary

The PR removes the notte agents command group, generated agent flags, validation, tests, and documentation while retaining session and function workflows.

• Removes agent command registration and agent-specific helpers.
• Removes agent state constants and code-generation mappings.
• Preserves cleanup compatibility for legacy current_agent files.
• Adds coverage for the removed command boundary and legacy-state cleanup.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the previously reported legacy agent-state cleanup issue is addressed at the current head.

Important Files Changed

Filename	Overview
internal/cmd/clear.go	The previous cleanup issue is fixed by explicitly deleting the legacy current_agent file while keeping agent functionality removed.
internal/cmd/clear_test.go	Adds focused coverage proving legacy agent state is removed and missing files are handled idempotently.
internal/cmd/agents.go	Removes the complete agent command group and its persisted-state helpers as intended.
internal/cmd/flags_test.go	Adds a public command-boundary test confirming agents are absent while sessions and functions remain registered.
internal/config/config.go	Removes agent-specific environment and state-file constants without preventing legacy cleanup.
scripts/gen-flags/parser.go	Removes the agent-start endpoint from generated CLI flag configuration.

_{Reviews (2): Last reviewed commit: "Address CI and PR review feedback" | Re-trigger Greptile}

[leo-notte]

@greptileai review

[giordano-lucas]

Linear: NOT-779 https://linear.app/nottelabsinc/issue/NOT-779/notte-cli-pr-64-remove-agents-from-notte-cli