[P2][SOC-02] User-controlled feed ranking

Programme: #1
Epic: #28

## Objective
Replace opaque engagement optimization with inspectable user-controlled ranking over the unified feed.

## Scope
- Chronological mode as a baseline.
- Source/account inclusion and weighting controls.
- Explicit interests, topic limits, recency, chosen diversity/exploration and muted themes.
- Ranking explanations: why this item appeared and which controls affected it.
- Persistent per-workspace/profile ranking preferences.
- Optional learned preferences only through MEM-01/MEM-02 rules.
- Deterministic reranking where possible; model-assisted classification remains evidence/feature input rather than hidden authority.
- A/B/evaluation against stated user goals, not session duration.

## Product rules
- Personalization changes relevance/presentation, not factual evidence.
- Users can always switch to chronological/source-specific views.
- Commercial relationships cannot silently influence ranking.

## Acceptance criteria
- [ ] User can inspect/change ranking controls and immediately see the effect.
- [ ] Every ranked item can expose a concise “why shown” explanation.
- [ ] Chronological mode behaves predictably without inference.
- [ ] Ranking preferences do not suppress source/evidence visibility or alter provider access rights.
- [ ] Inferred preferences follow MEM-02 consent/sensitivity rules.
- [ ] Ranking evaluation includes goal satisfaction and corrective interventions, not engagement-only metrics.

## Dependencies
- SOC-01
- MEM-01

**First phase:** P2
**Maturity target:** P5
**Owner:** connectors-domains

Start by reviewing the requirements in this issue and its dependencies, SOC-01, MEM-01, and MEM-02. Map the ranking controls, explanations, chronological mode, persistence, consent rules, and evaluation requirements to the existing feed entry points; done means all acceptance criteria are met without changing evidence visibility or provider access rights.

Written by the indexing model from the issue text.