feat(subs,gate): port agent concept

[michael-0acf4]

Continuation of #844

Note:
There is currently no need for additional flags when running typegate, existing runs should be picked automatically as long as the typegraph owning the workflow is deployed. SubstantialRuntime will launch and start the agent, the later will attempt to 'pick' jobs on the backend and spawn workers if it can acquire it.
Workflows are identified relative to their names for now, the content hash might be the way to go going forward, downside being that it will change even on smaller modifications (e.g. spaces, missing semicolons, ..).

Migration notes

None

• The change comes with new or modified tests
• Hard-to-understand functions have explanatory comments
• End-user documentation is updated to reflect the change

[codecov]

Codecov Report

Attention: Patch coverage is 88.14815% with 64 lines in your changes missing coverage. Please review.

Project coverage is 77.08%. Comparing base (c56803c) to head (4b0b13e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/typegate/src/runtimes/substantial/agent.ts	83.58%	54 Missing ⚠️
src/typegate/src/runtimes/substantial.ts	96.27%	7 Missing ⚠️
...rc/runtimes/substantial/workflow_worker_manager.ts	86.95%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #845      +/-   ##
==========================================
+ Coverage   77.04%   77.08%   +0.04%     
==========================================
  Files         147      148       +1     
  Lines       17226    17509     +283     
  Branches     1697     1721      +24     
==========================================
+ Hits        13271    13497     +226     
- Misses       3936     3993      +57     
  Partials       19       19              

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[michael-0acf4]

I will tackle Redis + making POLL_INTERVAL_SECONDS and LEASE_LIFESPAN_SECONDS configurable in another PR.