docs: repair flow assurance index

[EvenSol]

Closes part of #2499 (D007).

Frozen scan batch

• docs/pvtsimulation/flowassurance/README.md
• src/test/java/neqsim/pvtsimulation/flowassurance/FlowAssuranceDocumentationTest.java

This batch deliberately excludes docs/pvtsimulation/fluid_characterization_mathematics.md because open PR #2337 changes that page, and it does not overlap other open NeqSim PRs found during the scan.

Confirmed defects

Severity	Defect	Evidence / root cause
High	De Boer quick start did not compile	evaluateRisk() returns DeBoerRisk, not String
High	CPA onset example called a nonexistent API	ThermodynamicOperations.asphalteneOnsetPressure() does not exist; onset is implemented by AsphalteneOnsetPressureFlash
Medium	Corrosion navigation was broken	The page linked to nonexistent docs/process/corrosion/README.md; the section entry point is index.md
Medium	Screening-class table rendered incorrectly	A blockquote split the table before the scale and wax rows
Medium	Phase guidance overpromised behavior	Adding an asphaltene component does not by itself guarantee a precipitated phase or phase label
Medium	Onset classes were assigned to the wrong package	Both onset flashes live in neqsim.thermodynamicoperations.flashops.saturationops
Low	Jekyll title was duplicated	The front-matter title was repeated as an H1 contrary to the documentation agent rules
Low	Front-matter description was truncated	It ended in an ellipsis and omitted useful search terms

Fixes

• Reworked the page as a concise navigation and method-selection guide.
• Repaired the Markdown table and all internal targets in the frozen page.
• Replaced the broken quick start with the actual nested enum return type and documented deterministic output.
• Removed the nonexistent onset-operation call and pointed to the real flash classes and result API.
• Replaced unsupported fixed asphaltene-property claims with model- and calibration-aware guidance.
• Added explicit units, screening limitations, and links for hydrate, wax, erosion, emulsion, corrosion, scale, and asphaltene workflows.
• Added FlowAssuranceDocumentationTest to execute every API call in the remaining Java example.

Validation

Passed:

• Read current Java sources for all 14 classes named in the revised page.
• Confirmed all 17 relative documentation targets exist on current master.
• Confirmed the branch is exactly two files, two commits ahead of master, and not behind.
• Static Markdown checks: valid front matter, no duplicate H1, no \\(...\\) / \\[...\\] math delimiters, no HTML/Markdown mixing, balanced code fence.
• Runtime-smoked the complete quick start with NeqSim 3.16.0: MODERATE_PROBLEM, risk index 1.6.
• Hosted documentation build, source contracts, generated search coverage, and search JavaScript syntax.
• Hosted Javadoc, CodeQL, and agent-skill cross-reference checks.
• Scoped Spotless: the formatter reported no violation in FlowAssuranceDocumentationTest.
• Equation check: no equations remain in this landing page.
• External-link check: not applicable; the revised page contains no external links.
• Notebook check: not applicable; this batch contains no notebook.

Pending or blocked:

• The focused D007 JUnit has not executed on the hosted PR branch, so no JUnit pass is claimed. Repository-wide test compilation still stops first because PhaseAmmoniaEosTest.java:89 on current master neither catches nor declares IsNaNException; this is outside the two-file D007 diff.
• PR Fix ammonia EOS test compilation #2524 proposes the exact checked-exception and formatter-only repairs without overlapping D007. On its head, pre-commit, Spotless, Javadoc, CodeQL, and agent-skill checks pass, proving the original compile/format gates are repaired.
• PR Fix ammonia EOS test compilation #2524's Windows matrix then executed 10,526 tests and reported nine unrelated failures in RCA, field-lifecycle, LNG, and ammonia tests; the Ubuntu matrix was canceled after the Windows failure. D007 does not change those systems and will not absorb their fixes.
• A local focused-Maven attempt was not completed because the runner had no dependency cache and external Maven artifact access was unavailable; it is not counted as validation evidence.
• The page has not been visually inspected in a browser. Hosted Jekyll build and search rendering gates passed, but no screenshot is claimed.

Expected regression result

The quick-start inputs P_res = 350 bara, P_sat = 150 bara, and rho = 750 kg/m3 should return:

• DeBoerRisk.MODERATE_PROBLEM
• risk index 1.6

The focused JUnit test locks both values.

Next D007 step

Keep this PR draft. After #2524 or an equivalent repair lands on master, rerun the focused D007 JUnit and full matrix; distinguish any remaining repository-wide failures from the two-file documentation batch. No production code is changed.