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relates to GRU-18
Adds basic implementation for Workspace Agent Connection Watch and tests.
Missing are handling of logs.
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relates to GRU-18
Adds support for tailnet updates to Tunneler FSM.
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relates to GRU-18
Adds support for network application (e.g. SSH) updates to Tunneler.
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relates to GRU-18
Adds support for agent updates to the Tunneler
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Adds the Tunneler state machine and logic for handling build updates.
This is a partial implementation and tests. Further PRs will fill out
the other event types.
Relates to GRU-18