fix(tools): name a missing dependency and a dependency cycle in resolve.py errors (#1922)

[braboj]

Closes #1922.

What

• tools/resolve.py: a shared _resolve_order walker now backs both resolve_chain and resolve_ids. It raises ResolveError with one of three messages:
  • Missing dependency: <entry> depends on <id>, which has no manifest entry, or the core tier names <id>… when the missing ID comes from the core list
  • Dependency cycle: a -> b -> a
  • Unknown root: <id> has no manifest entry, for library callers. The CLI still checks the root itself first.
• main() prints the message and exits 1 with no traceback. The old code dropped a missing ID and resolved a shorter chain at exit 0, and recursed on a cycle until RecursionError.
• SYS-19 (new smoke check, with spec SAIT-SMK-SYS-19-001A and an INDEX row): it plants a manifest with a valid control root, a missing ID and a cycle, then runs the resolver's own main() against each one. It asserts the status, the phrase, and that no traceback appears.
• CLAUDE.md §5.2 lists SYS-19. CHANGELOG has an Unreleased "Added" line (forks run resolve.py).

Behaviour unchanged on the real manifest

Every root from --roots plus both fixtures resolves to byte-identical output before and after: 39 roots, 586 lines. --roots output is identical too, and resolve.py --check passes.

Verification

• run_smoke.py: 34/34. sync.py --check and audit_redundancy.py --check are clean. run_conformance.py: 0 failed. Its readings: release ordering has no other ready PR, no off-limits path is touched, and the test change is tests/run_smoke.py gaining SYS-19 (pure addition).
• Control: SYS-19 against main's resolve.py (confirmed landed) fails. stack-missing exits 0, and stack-cycle exits 1 without the cycle phrase. Then reverted.

🤖 Generated with Claude Code

[braboj]

Review finding addressed in f4ea0f4 "check the core tier's own dependencies in resolve.py":

• _resolve_order now runs _check_graph over the core tier's subgraph before it checks the root's tree. Seeding the core tier as done for ordering left the core entries' own depends_on unwalked. The output order is unchanged: the core tier first, in manifest order, then the root's chain.
• SYS-19 plants one manifest per core-tier fault, since such a fault breaks every root. The three new cases are core → missing, core → core, and core → stack → core. Each now exits 1 with Missing dependency: base-a depends on base-nowhere, Dependency cycle: base-a -> base-a or Dependency cycle: base-a -> stack-valid -> base-a. That makes 6 cases in all.
• Control: SYS-19 against the previous walker (confirmed landed) fails exactly those three cases, each at exit 0. Then reverted.
• All 39 roots plus both fixtures still resolve to byte-identical output against main. resolve.py --check passes, smoke 34/34, sync and the redundancy audit are clean, and conformance has 0 failed.