feat(i18n): translate agents.json chapter to Brazilian Portuguese

Fill the `pt` mirror fields on the /agents/ chapter so the bilingual
contract stops being silently English-only. 24 fields: hero eyebrow,
title, lede, three role cards (FRAME/HAND OFF/PROVE), and two
sections (the worktree-map panel and the handoff steps).

The chapter adds two shapes that the prior translations did not need:
the FRAME/HAND OFF/PROVE chip labels (uppercase action verbs in the
source) and the tree-drawing `panelCode` block. Both translate
cleanly:

- Chip labels become imperative Portuguese verbs in caps —
  ENQUADRAR, PASSAR, COMPROVAR — matching the DIAGNOSTICAR pattern
  already established by commonSkills/debug.json.
- Tree-drawing characters (├──, └──, │) in panelCode are
  language-neutral and preserved byte-for-byte. The English and
  Portuguese forms are visually parallel at every column.

Translation register follows the conventions established by
src/content/commonSkills/*.json, the full-guide PT snapshot, and
the three prior commits on this branch (1baa314 landing.json,
fd031b0 summary.json, 160a324 models.json): imperative voice,
second-person `você`, sentence-case prose, all-caps labels, and
English kept for product nouns (skill, worktree, brief, gate,
pipeline, recall, prompt, enforcement, runs, orchestrator). `Worker`
becomes `Agente` because the card title is a prose role-noun (per
the glossary rule: worker in tab labels and code-like fragments,
agente in prose). `Brief` (the handoff step) stays English as a
product noun. `Passagem` for "Handoff" follows full-guide-pt.json.

Verified by .agents/scripts/audit-translations.mjs: agents.json
contribution to the offenders list drops from 24 to 0 (one field,
`steps.0.label` for "Brief", remains identical by design — Brief is
a product noun and is intentionally kept in English). Remaining
identical fields live in skills.json (16) and the 7-each numeric
card-label residues in landing.json and summary.json, which land in
subsequent commits.

The English side is byte-identical to origin/main, including the
tree-drawing panelCode. Confirmed via byte-level diff before commit.

src/content/chapters/agents.json

@@ -2,57 +2,57 @@
   "id": "agents",
   "eyebrow": {
     "en": "Subagent workflow",
-    "pt": "Subagent workflow"
+    "pt": "Fluxo de subagentes"
   },
   "title": {
     "en": "One branch<br>per <em>hand.</em>",
-    "pt": "One branch<br>per <em>hand.</em>"
+    "pt": "Uma branch<br>por <em>mão.</em>"
   },
   "lede": {
     "en": "Agents work when roles, files, and evidence are bounded. A worktree gives each worker its own checkout while the orchestrator protects intent.",
-    "pt": "Agents work when roles, files, and evidence are bounded. A worktree gives each worker its own checkout while the orchestrator protects intent."
+    "pt": "Agentes funcionam quando papéis, arquivos e evidências são delimitados. Um worktree dá a cada agente seu próprio checkout enquanto o orquestrador protege a intenção."
   },
   "cards": [
     {
       "label": {
         "en": "FRAME",
-        "pt": "FRAME"
+        "pt": "ENQUADRAR"
       },
       "title": {
         "en": "Orchestrator",
-        "pt": "Orchestrator"
+        "pt": "Orquestrador"
       },
       "copy": {
         "en": "Owns scope, task graph, boundaries, and integration.",
-        "pt": "Owns scope, task graph, boundaries, and integration."
+        "pt": "Dono do escopo, do grafo de tarefas, das fronteiras e da integração."
       }
     },
     {
       "label": {
         "en": "HAND OFF",
-        "pt": "HAND OFF"
+        "pt": "PASSAR"
       },
       "title": {
         "en": "Worker",
-        "pt": "Worker"
+        "pt": "Agente"
       },
       "copy": {
         "en": "Owns one coherent slice and one worktree.",
-        "pt": "Owns one coherent slice and one worktree."
+        "pt": "Dono de uma fatia coerente e de um worktree."
       }
     },
     {
       "label": {
         "en": "PROVE",
-        "pt": "PROVE"
+        "pt": "COMPROVAR"
       },
       "title": {
         "en": "Verifier",
-        "pt": "Verifier"
+        "pt": "Verificador"
       },
       "copy": {
         "en": "Re-runs gates and reports remaining gaps.",
-        "pt": "Re-runs gates and reports remaining gaps."
+        "pt": "Roda gates novamente e reporta o que ainda falta."
       }
     }
   ],
@@ -60,29 +60,29 @@
     {
       "eyebrow": {
         "en": "The tree",
-        "pt": "The tree"
+        "pt": "A árvore"
       },
       "title": {
         "en": "Split at<br>the <em>seam.</em>",
-        "pt": "Split at<br>the <em>seam.</em>"
+        "pt": "Divida na<br><em>costura.</em>"
       },
       "panelLabel": {
         "en": "MAIN / ORCHESTRATOR",
-        "pt": "MAIN / ORCHESTRATOR"
+        "pt": "MAIN / ORQUESTRADOR"
       },
       "panelCode": {
         "en": "├── agent/ui    → components + visual states\n├── agent/tests → acceptance + regressions\n└── agent/docs  → guide + examples\n\nmerge after each leaf returns a diff and evidence",
-        "pt": "├── agent/ui    → components + visual states\n├── agent/tests → acceptance + regressions\n└── agent/docs  → guide + examples\n\nmerge after each leaf returns a diff and evidence"
+        "pt": "├── agent/ui    → componentes + estados visuais\n├── agent/tests → aceitação + regressões\n└── agent/docs  → guia + exemplos\n\nfaça merge depois que cada folha devolver um diff e evidências"
       }
     },
     {
       "eyebrow": {
         "en": "Handoff",
-        "pt": "Handoff"
+        "pt": "Passagem"
       },
       "title": {
         "en": "Context that<br>can <em>travel.</em>",
-        "pt": "Context that<br>can <em>travel.</em>"
+        "pt": "Contexto que<br>pode <em>viajar.</em>"
       },
       "steps": [
         {
@@ -92,27 +92,27 @@
           },
           "copy": {
             "en": "Goal, owned files, dependencies, non-goals, acceptance.",
-            "pt": "Goal, owned files, dependencies, non-goals, acceptance."
+            "pt": "Objetivo, arquivos sob sua posse, dependências, fora de escopo, aceitação."
           }
         },
         {
           "label": {
             "en": "Isolation",
-            "pt": "Isolation"
+            "pt": "Isolamento"
           },
           "copy": {
             "en": "One branch and worktree per independent change.",
-            "pt": "One branch and worktree per independent change."
+            "pt": "Uma branch e um worktree por mudança independente."
           }
         },
         {
           "label": {
             "en": "Evidence",
-            "pt": "Evidence"
+            "pt": "Evidência"
           },
           "copy": {
             "en": "Commands, result, changed files, screenshots, gaps.",
-            "pt": "Commands, result, changed files, screenshots, gaps."
+            "pt": "Comandos, resultado, arquivos alterados, capturas de tela, lacunas."
           }
         }
       ]