docs(changelog): model-status accuracy, max-level caveats, contributor credit, voice

- gpt-5.2 is deprecated but still selectable (survived the 2026-04-14 Codex
  retirement wave; no API shutdown for the base model) — only gpt-5.1-codex-max
  is retired (API shutdown 2026-07-23). Entry no longer calls both 'retired'.
- max escape hatch now carries the codex >= 0.144 + explicit-5.6-model caveats;
  notes the ultra tier above max.
- Adds 'Contributed by @cathrynlavery' per repo convention.
- Release-summary prose aligned with voice rules (no em dashes).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -5,7 +5,7 @@
 ## **`/codex` docs now point at the GPT-5.6 family and name the new `max` reasoning level.**
 ## **No behavior change: /codex still auto-uses whatever Codex's frontier default is.**
 
-The `/codex` skill never hardcodes a model on purpose — it rides whatever Codex ships as its current frontier default, so it picks up new models the day they land. This release refreshes the skill's documentation to match the July 2026 lineup: the illustrative `-m` examples and the "Model & Reasoning" section now reference the GPT-5.6 family (`sol` > `terra` > `luna`, with bare `gpt-5.6` aliasing to `sol`) instead of the retired `gpt-5.1-codex-max` / `gpt-5.2` names, and the reasoning-effort docs now cover the new `max` level that 5.6 adds above `xhigh`. Defaults, flags, and the `--xhigh` override are unchanged.
+The `/codex` skill never hardcodes a model on purpose. It rides whatever Codex ships as its current frontier default, so it picks up new models the day they land. This release refreshes the skill's documentation to match the July 2026 lineup: the illustrative `-m` examples and the "Model & Reasoning" section now reference the GPT-5.6 family (`sol` > `terra` > `luna`; the bare `gpt-5.6` API alias routes to `sol`) instead of `gpt-5.1-codex-max` (retired from Codex, API shutdown 2026-07-23) and `gpt-5.2` (deprecated but still selectable), and the reasoning-effort docs now cover the new `max` level that 5.6 adds above `xhigh`. Defaults, flags, and the `--xhigh` override are unchanged.
 
 ### The GPT-5.6 numbers that matter
 
@@ -17,17 +17,17 @@ Source: OpenAI's GPT-5.6 launch materials and the OpenRouter API listing (July 2
 | `gpt-5.6-terra` | 1.05M (128k out) | $2.50 / $15 | Balanced everyday model |
 | `gpt-5.6-luna` | 1.05M (128k out) | $1 / $6 | Fast and affordable |
 
-Reasoning-effort levels are now `none`, `low`, `medium`, `high`, `xhigh`, `max`. gstack still defaults Review/Challenge to `high` and Consult to `medium`, and wires no flag for `max` (pass `-c model_reasoning_effort=max` by hand if you truly need it).
+Reasoning-effort levels on GPT-5.6 are `none`, `low`, `medium`, `high`, `xhigh`, `max` (an `ultra` tier above `max` appears on some surfaces). gstack still defaults Review/Challenge to `high` and Consult to `medium`, and wires no flag for `max`. To use it by hand you need codex CLI 0.144 or newer and an explicit GPT-5.6 model: `-m gpt-5.6-sol -c model_reasoning_effort=max`. Older CLIs reject the value.
 
 ### What this means for you
 
-Nothing changes in how `/codex` runs — it was already using 5.6 the moment it became Codex's default. The docs just stop pointing at dead model names, so when you reach for `-m` you see the models that actually exist today.
+Nothing changes in how `/codex` runs. It picks up GPT-5.6 as soon as Codex makes it the default. The docs just stop pointing at superseded model names, so when you reach for `-m` you see the current lineup.
 
 ### Itemized changes
 
 #### Changed
 
-- `codex/SKILL.md` (+ template): Model & Reasoning section names the GPT-5.6 family as the current frontier; `-m` examples updated from `gpt-5.1-codex-max` / `gpt-5.2` to `gpt-5.6-sol` / `gpt-5.6-luna`; documented the new `max` reasoning-effort level above `xhigh`. No change to the no-hardcode default or the per-mode reasoning defaults.
+- `codex/SKILL.md` (+ template): Model & Reasoning section names the GPT-5.6 family as the current frontier; `-m` examples updated from `gpt-5.1-codex-max` / `gpt-5.2` to `gpt-5.6-sol` / `gpt-5.6-luna`; documented the new `max` reasoning-effort level above `xhigh`, including the CLI-version (codex >= 0.144) and explicit-5.6-model caveats needed to actually use it. No change to the no-hardcode default or the per-mode reasoning defaults. Contributed by @cathrynlavery.
 
 ## [1.58.5.0] - 2026-06-21