docs(#1847): add Claude Sonnet 5 changeset for next-line changelog + refresh stale model examples

The 1.6.1 forward-port (#1851) used the no-changelog opt-out instead of carrying
a changeset, so Sonnet 5 — unlike every other 1.6.1 fix (#1580/#1591/#1693 whose
fragments live on next) — had no fragment and would be MISSING from the 1.7.0
changelog. Add the fragment so the release render reflects current shipping code.
Also note the bold-checklist form in the #1591 fragment, and refresh two stale
claude-sonnet-4-6 illustrative examples to current IDs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.changeset/1591-phase-complete-details-wrapped-checklist.md

@@ -2,5 +2,5 @@
 type: Fixed
 pr: 1819
 ---
-**`phase.complete` no longer reports a false `is_last_phase` on a `<details>`-wrapped checkbox checklist (#1591, #1752)** — when the active milestone's phase checklist was written as `- [ ] Phase N:` checkbox items inside a `<details>` block and the next phase had no directory on disk yet (still in planning), `phase.complete`'s `isLastPhase` roadmap-enumeration fallback used a heading-only pattern (`/#{2,4}\s*Phase…/`) that never matched checkbox items. It returned `is_last_phase: true, next_phase: null` on a mid-milestone phase and — via the milestone-complete cascade — wrongly flipped STATE.md to `Milestone complete` and decremented `progress.total_phases` (e.g. 8 → 7). The pattern now matches both heading-style (`### Phase N:`) and checkbox-list phases (`- [ ] Phase N:` / `- [x] Phase N:`); `extractCurrentMilestone` already surfaces the `<details>`-wrapped checklist correctly, so no parser change was needed. Only the reproduced `phase.complete` fallback is changed; the heading-only sibling patterns elsewhere in `phase.cts` are untouched.
+**`phase.complete` no longer reports a false `is_last_phase` on a `<details>`-wrapped checkbox checklist (#1591, #1752)** — when the active milestone's phase checklist was written as `- [ ] Phase N:` checkbox items inside a `<details>` block and the next phase had no directory on disk yet (still in planning), `phase.complete`'s `isLastPhase` roadmap-enumeration fallback used a heading-only pattern (`/#{2,4}\s*Phase…/`) that never matched checkbox items. It returned `is_last_phase: true, next_phase: null` on a mid-milestone phase and — via the milestone-complete cascade — wrongly flipped STATE.md to `Milestone complete` and decremented `progress.total_phases` (e.g. 8 → 7). The pattern now matches heading-style (`### Phase N:`), plain checkbox-list phases (`- [ ] Phase N:` / `- [x] Phase N:`), and the canonical **bold** checklist form the roadmap template emits (`- [ ] **Phase N: Name**`); `extractCurrentMilestone` already surfaces the `<details>`-wrapped checklist correctly, so no parser change was needed. Only the reproduced `phase.complete` fallback is changed; the heading-only sibling patterns elsewhere in `phase.cts` are untouched.
 

.changeset/1847-claude-sonnet-5-standard-tier.md

@@ -0,0 +1,5 @@
+---
+type: Added
+pr: 1848
+---
+**Claude Sonnet 5 is now the `standard` (sonnet) tier model.** The model catalog and provider presets resolve the sonnet/standard tier to `claude-sonnet-5` (GA 2026-06-30) across the Anthropic-backed runtimes (`claude`, `copilot`, and the `anthropic`/`anthropic-fable` presets), plus the OpenRouter-style `anthropic/claude-sonnet-5` for `opencode`/`hermes`, replacing the superseded `claude-sonnet-4-6`. Opus and Haiku tier defaults are unchanged (the `haiku` high-effort preset's escalation slot tracks the current sonnet model). Shipped in 1.6.1. (#1847) (#1848)

agents/gsd-ai-researcher.md

@@ -72,7 +72,7 @@ Update AI-SPEC.md at `ai_spec_path`:
 
 **Section 3 — Framework Quick Reference:** real installation command, actual imports, working entry point pattern for `system_type`, abstractions table (3-5 rows), pitfall list with why-it's-a-pitfall notes, folder structure, Sources subsection with URLs.
 
-**Section 4 — Implementation Guidance:** specific model (e.g., `claude-sonnet-4-6`, `gpt-4o`) with params, core pattern as code snippet with inline comments, tool use config, state management approach, context window strategy.
+**Section 4 — Implementation Guidance:** specific model (e.g., `claude-sonnet-5`, `gpt-4o`) with params, core pattern as code snippet with inline comments, tool use config, state management approach, context window strategy.
 </step>
 
 <step name="write_section_4b">

gsd-core/workflows/execute-phase.md

@@ -84,7 +84,7 @@ AGENT_SKILLS=$(gsd_run query agent-skills gsd-executor)
 
 Parse JSON for: `executor_model`, `verifier_model`, `commit_docs`, `parallelization`, `branching_strategy`, `branch_name`, `phase_found`, `phase_dir`, `phase_number`, `phase_name`, `phase_slug`, `plans`, `incomplete_plans`, `plan_count`, `incomplete_count`, `state_exists`, `roadmap_exists`, `phase_req_ids`, `response_language`.
 
-**Model resolution:** If `executor_model` is `"inherit"`, omit the `model=` parameter from all `Agent()` calls — do NOT pass `model="inherit"` to Agent. Omitting the `model=` parameter causes Claude Code to inherit the current orchestrator model automatically. Only set `model=` when `executor_model` is an explicit model name (e.g., `"claude-sonnet-4-6"`, `"claude-opus-4-7"`).
+**Model resolution:** If `executor_model` is `"inherit"`, omit the `model=` parameter from all `Agent()` calls — do NOT pass `model="inherit"` to Agent. Omitting the `model=` parameter causes Claude Code to inherit the current orchestrator model automatically. Only set `model=` when `executor_model` is an explicit model name (e.g., `"claude-sonnet-5"`, `"claude-opus-4-8"`).
 
 **If `response_language` is set:** Include `response_language: {value}` in all spawned subagent prompts so any user-facing output stays in the configured language.