enhance(#2229): add three-way claim disposition (admit/refute/abstain) to /gsd-explore research pass (#2543)

Closes #2229.

Each claim surfaced by /gsd-explore's research pass is dispositioned admit, refute, or abstain, with abstentions routed to a visible ledger instead of being smoothed into confident prose. Refute and abstain are separated by whether the disagreeing source is authoritative for that claim; a strong prior is never authoritative alone.

Two guards ride with it: conflict-abstention, and a tier floor that presents a would-be admit as an abstain when the researcher's resolved tier is the budget tier or cannot be determined.

To make that floor enforceable, resolve-model now emits the effective tier (--pick tier). It was already computed above the resolve_model_ids omit gate but was unreachable from a workflow, which left the floor inert on every non-Claude install - the model id is blank under omit and runtime-substituted where a tier map exists, and the profile defaults to balanced. The tier signal mirrors every resolution step that can change which tier runs, including the model_policy preset, and reports unknown rather than guessing. Output is additive; model, profile and effort are unchanged.

Two residuals are disclosed in the workflow rather than papered over: a raw-model-id model_overrides pin reports unknown and is floored (fails closed), and a model_profile_overrides entry repointing a tier at another tier's model can under-report (fails open, and predates this change).

Admin merge used only to satisfy the missing secondary reviewer on a single-maintainer PR. No CI failure and no conflict were bypassed: 38 checks green, remote runner 32255/32255 on both Node lanes.

docs/COMMANDS.md

@@ -788,6 +788,8 @@ Socratic ideation session — guide an idea through probing questions, optionall
 /gsd-explore authentication strategy  # Explore a specific topic
 ```
 
+When the optional research pass runs, each surfaced claim is dispositioned three ways — **admit** (survives a prompted-to-refute pass and is grounded in a source, shown with the source), **refute** (a source *authoritative for that claim* contradicts it, dropped or corrected), or **abstain** (unverifiable, non-authoritative disagreement, or a source-vs-prior conflict). Abstained claims are listed in a separate **Unresolved** ledger rather than smoothed into the narrative. (Claims-side analogue of the honest verifier, #1154.)
+
 ---
 
 ### `/gsd-undo`

docs/CONFIGURATION.md

@@ -1530,6 +1530,18 @@ The intent is the same as the Claude profile tiers -- use a stronger model for p
 | `true` | Maps aliases to full Claude model IDs (`claude-opus-4-8`) | Claude Code with API that requires full IDs |
 | `"omit"` | Returns empty string (runtime picks its default) | Non-Claude runtimes (Codex, OpenCode, Antigravity CLI, Kilo) |
 
+### The `tier` Field
+
+`node gsd-tools.cjs query resolve-model <agent> --pick tier` returns the tier GSD resolved for that agent, independent of `resolve_model_ids`: `opus` | `sonnet` | `haiku` | `fable` | `inherit` | `unknown`. It is also emitted as a `tier` key in the command's full JSON output.
+
+`tier` is computed above the `resolve_model_ids: "omit"` gate, so it stays meaningful exactly where `model` does not — every non-Claude install (blank under `"omit"`) and any install where the runtime's tier map substitutes a name (e.g. `gpt-5.6-luna` for the haiku tier on Codex).
+
+`tier` accounts for every step that can change which tier runs, including a `model_policy` preset — a preset resolves after the profile tier and can dispatch a different one, so `model_policy: {provider: anthropic, budget: low}` under a `balanced` profile reports `haiku`, not `sonnet`.
+
+**Honesty semantics:** a `model_overrides` pin naming a known alias or a mappable full Claude id reports that alias; a pin to an unmappable raw model id reports `unknown`; a policy-resolved model that maps to no alias — including every non-Claude runtime, where the policy model is passed through verbatim — reports `unknown` rather than falling back to the profile tier; `model_profile: inherit` reports `inherit`; an agent with no catalog entry reports `unknown`. `tier` never guesses, so treat `unknown` and `inherit` as *cannot tell*, never as *adequate*.
+
+**One limit:** a `model_profile_overrides.<runtime>.<tier>` entry that repoints a tier at another tier's model makes `tier` report the tier that was asked for, not the tier of the model that answers.
+
 ### Runtime-Aware Profiles (#2517)
 
 When `runtime` is set, profile tiers (`opus`/`sonnet`/`haiku`) resolve to runtime-native model IDs instead of Claude aliases. This lets a single shared `.planning/config.json` work cleanly across Claude and Codex.

docs/FEATURES.md

@@ -2222,6 +2222,7 @@ Test suite that scans all agent, workflow, and command files for embedded inject
 - REQ-EXPLORE-02: Session MUST offer to route outputs to the appropriate GSD artifact
 - REQ-EXPLORE-03: An optional topic argument MUST prime the first question
 - REQ-EXPLORE-04: Exploration MUST optionally spawn a research agent for technical feasibility
+- REQ-EXPLORE-05: A research pass MUST disposition each surfaced claim (admit / refute / abstain) and route every abstention to a visible Unresolved Ledger — never smoothing an ungrounded claim into the narrative as confident prose
 
 ---