Introduce NeqSim Studio alongside Classic

[EvenSol]

Summary

First tranche of the new NeqSim Web Studio Campaign, superseding the former Process Flowsheet Studio schedule without restarting its mature implementation.

• preserve the existing NeqSim Web homepage content and sidebar-driven Classic workflow
• add an explicit Studio vs Classic workspace choice without moving existing Classic pages
• add a separate professional NeqSim Studio (Beta) dashboard
• make the existing validated pages/35_Process_Flowsheet_Studio.py the first enabled Studio engineering workflow
• expose Thermodynamics & PVT, Equipment Design, Engineering Studies, Dynamics, Engineering Drawings, Process Chat and Examples with honest planned/core-in-progress states
• add a declarative Studio navigation contract instead of duplicating calculation logic
• add docs/neqsim_web_studio_roadmap.md defining the three-repository architecture and inherited Process Flowsheet Studio foundation
• extend the existing Process Flowsheet Studio GitHub Actions gate so Classic/Studio shell changes receive hosted compile, Streamlit AppTest, real HTTP/health, and inherited simulation-regression coverage
• correct Classic developer links to the actual EvenSol/neqsimweb2 repository

Product boundary

Classic remains available. Existing users can continue using the current pages, calculations, saved cases and sidebar workflow. Studio is introduced side-by-side and is explicitly labelled Beta.

Studio does not create a second simulation engine:

• equinor/neqsim: authoritative thermodynamics, process simulation, design, dynamics, optimization and PFD/P&ID/DEXPI semantics
• EvenSol/neqsimweb2: Classic + Studio UI, orchestration and shared adapters
• EvenSol/NeqSim-Colab: executable reference workflows and acceptance evidence

The active NeqSim ISO PFD (#1332) and DEXPI/P&ID (#2899) campaigns remain authoritative for drawing semantics; this PR deliberately does not implement a competing diagram engine.

Inherited foundation

The new campaign inherits the merged Process Flowsheet Studio work: generic graph/schema execution, explicit named streams/ports, multiple feeds, mixers/splitters/phase outlets, workbooks, studies, equipment design, subflowsheets, persistence, Process Chat handoff, convergence/conservation evidence, timeout/fail-loud behavior and deployment hardening.

Validation

Exact head: 4e2db28de200a335ca1f9cd34d994c51236e512d

Local source validation:

• Python compilation of the new/changed Studio shell and navigation sources — passed
• PYTHONPATH=. python tests/test_studio_navigation.py -v — 4/4 passed

Hosted GitHub Actions Process Flowsheet Studio #384, run 31332379742, completed successfully on the exact head. All steps passed:

• install native NeqSim / Streamlit / required web dependencies
• compile affected Python sources
• Studio workspace navigation regressions
• Studio shell Streamlit AppTest
• Classic and Studio real HTTP health regressions: both entry points launch as Streamlit servers, root returns HTTP 200, /_stcore/health returns ok on repeated probes, and the process remains live
• deployment-safe import regressions
• warm-deployment Streamlit smoke test
• draft graph editor regressions
• named material stream regressions
• solver diagnostic adapter tests
• subflowsheet schema regressions
• native multi-inlet conservation benchmark
• bounded execution regressions

Branch/diff evidence:

• 11 commits ahead / 0 behind main
• 9 intended files only
• PR is mergeable
• no review or inline review threads are open on the exact head
• no NeqSim Java or NeqSim-Colab modification is required for this S0/S1 tranche

Roadmap

Advances:

• S0 — Classic preservation and architecture baseline
• S1 — Studio shell and workspace choice

Next largest safe tranche after merge: establish the shared Studio case context/lifecycle, then integrate the mature Process Flowsheet Studio behind that context rather than rewriting it.

Documentation impact

Adds the persistent Studio roadmap/architecture ledger. Classic user documentation remains in place; only incorrect web-repository URLs are corrected.