fix(topology): read block dependencies from local pipeline YAML

[loadez]

Problem

sem-ai critical-path and sem-ai pipeline topology reported every block with no dependencies, so the critical path was always a single block (depth 1) regardless of the real DAG.

Root cause is in fetchTopology: it only tries to obtain the pipeline YAML by fetching it as a workflow artifact (.semaphore/semaphore.yml). But the pipeline definition isn't a job artifact, so that fetch always misses — and the v1alpha pipeline-describe response carries block name/state/result but no dependency info. With no YAML, every block fell back to dependencies: [].

Fix

• cmd/topology_commands.go — add a local fallback (localPipelineDeps): when the artifact fetch yields nothing, read the pipeline YAML from the working tree (<working_dir>/<yaml_file>, default .semaphore/semaphore.yml) and parse block dependencies. This is the common case — you run critical-path from the repo, where the YAML lives. The result's source field now reports v1alpha+artifact / v1alpha+local / v1alpha+none for transparency.
• cmd/topology_test.go — regression test (TestLocalPipelineDeps): writes a .semaphore/semaphore.yml with a Build→Test→Deploy chain, asserts deps parse and computeCriticalPath returns the full 3-block chain; missing file → nil.

The existing parseYAMLDependencies / computeCriticalPath units were already correct and tested — the gap was purely that the YAML was never read.

Verification

Against a real 6-block pipeline (Build → {Unit, Race, Vet} → Integration → Package):

before: { "critical_path": ["Build"], "depth": 1 }
after:  { "critical_path": ["Build","Unit tests","Integration","Package"], "depth": 4, "total_blocks": 6 }

go test ./..., go vet ./... pass.

Tracking

renderedtext/project-tasks#3414