feat(monorepo): detect dependency cycles and release in topological order

[BryanFRD]

Closes #418.

dependsOn was handled as a flat list with no cycle behaviour: the dependency cascade simply capped its fixed-point loop at packages.len() rounds to avoid spinning forever, so a cyclic config silently produced an incorrect/partial result instead of a clear error.

This adds a single graph pass (Tarjan SCC) over the package dependency graph, run at the very top of run_release_logic — before any git work, lock, or write — so it covers both ferrflow check and ferrflow release and can never leave a partial release behind:

• Cycle detection. Any strongly-connected component with more than one member (or a package depending on itself) is a cycle. The error names the loop, e.g. cycle detected: api → web → api, and carries error code E8003 (MONOREPO_DEPENDENCY_CYCLE).
• Topological ordering. When the graph is acyclic, the same pass yields a dependencies-first release order (a dependency is released before the packages that depend on it). Packages without any dependsOn keep their config order, so existing behaviour is unchanged for the common case.

Tests

• graph.rs unit tests: identity order with no deps, dependency-before-dependent, linear chain, unknown-dependency names ignored, two-package cycle, self-dependency, three-package cycle path rendering.
• Integration test (cycle_detection): two packages depending on each other → a real (non-dry-run) release aborts with E8003, the message names both packages, no panic, and both version files are left untouched (no partial release).

Full suite green (858 + 668 tests), cargo fmt + clippy clean.

Docs

In-repo docs/errors.md gains the E8003 entry. The public docs-site monorepo page + errors reference are updated in a companion FerrFlow-Cloud PR (cross-repo changes are kept separate).

[github-actions]

Benchmark

Details

Benchmark suite	Current: 042a7e6	Previous: 0b5fe57	Ratio
full_check_flow/100_commits	5489553 ns/iter (± 157149)
full_check_flow/1000_commits	51558258 ns/iter (± 644307)

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