fix(agent-service): align auto-layout rank separation

[officialasishkumar]

What changes were proposed in this PR?

The agent service and frontend both use dagre for workflow auto-layout, but the agent service used ranksep: 100 while the frontend uses rankSep: 80. That made agent-generated layouts wider than layouts produced by the frontend auto-layout button.

This PR updates the agent-service layout config to ranksep: 80 and adds a regression test that pins the produced two-node spacing to the frontend-equivalent value.

Any related issues, documentation, discussions?

Closes #4577.

How was this PR tested?

Installed agent-service dependencies from bun.lock in the worktree, then ran:

npm_config_cache=/tmp/texera-npm-cache npx --yes bun@1.3.3 test src/agent/util/auto-layout.test.ts

Result: 7 passed.

npm_config_cache=/tmp/texera-npm-cache npx --yes bun@1.3.3 run typecheck

Result: passed.

npm_config_cache=/tmp/texera-npm-cache npx --yes bun@1.3.3 run format:check

Result: passed.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: OpenAI Codex (GPT-5)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.65%. Comparing base (e7e5d4e) to head (c3bf588).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #5176   +/-   ##
=========================================
  Coverage     43.65%   43.65%           
  Complexity     2219     2219           
=========================================
  Files          1049     1049           
  Lines         40572    40572           
  Branches       4324     4324           
=========================================
  Hits          17713    17713           
  Misses        21767    21767           
  Partials       1092     1092           

Flag	Coverage Δ		*Carryforward flag
access-control-service	39.53% <ø> (ø)		Carriedforward from e7e5d4e
agent-service	33.76% <100.00%> (ø)
amber	44.04% <ø> (ø)		Carriedforward from e7e5d4e
computing-unit-managing-service	0.00% <ø> (ø)		Carriedforward from e7e5d4e
config-service	0.00% <ø> (ø)		Carriedforward from e7e5d4e
file-service	32.18% <ø> (ø)		Carriedforward from e7e5d4e
frontend	35.15% <ø> (ø)		Carriedforward from e7e5d4e
python	90.50% <ø> (ø)		Carriedforward from e7e5d4e
workflow-compiling-service	56.81% <ø> (ø)		Carriedforward from e7e5d4e

*This pull request uses carry forward flags. Click here to find out more.

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[Yicong-Huang]

LGTM