bruno: replace Python generator with Go golden-writer in the drift test

The generator moves into the Go toolchain per repo preference:
internal/docs/bruno_gen.go emits the OpenCollection mirrors (same output
contract — gate-verified example-request bodies, env-var params,
device-token headers, login/register/refresh token-capture scripts) and
TestBrunoMirrorsDocs grows a -update flag: verification by default,
regeneration on demand:

  go test ./internal/docs -run TestBrunoMirrorsDocs -update

Generator and checker are now the same code — they cannot drift apart.
scripts/gen_bruno_from_docs.py deleted; opencollection.yml README points
at the go-test command.

Also fixed vs the Python pass: mirror placement follows the docs tree
folder (RelPath), not the area frontmatter (several docs — highlights,
notes, ratings, users, progress — carry a different area); docs blocks
emit the collection's mapping form (content + type), not a bare scalar;
JSON body sanity is checked at generation time.

Idempotent: back-to-back -update runs are byte-identical.
make test green (9 pkgs).

bruno/koreader/get_library.yml

@@ -16,9 +16,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Get Library
+docs:
+  content: |-
+    # Get Library
 
-  `GET /api/sync/koreader/library` — auth: device-token.
+    `GET /api/sync/koreader/library` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/get_library.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/get_library.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/get_metadata.yml

@@ -16,9 +16,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Get Metadata
+docs:
+  content: |-
+    # Get Metadata
 
-  `GET /api/sync/koreader/metadata/:uuid` — auth: device-token.
+    `GET /api/sync/koreader/metadata/:uuid` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/get_metadata.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/get_metadata.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/get_rating.yml

@@ -16,9 +16,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Get KOReader Rating
+docs:
+  content: |-
+    # Get KOReader Rating
 
-  `GET /api/sync/koreader/rating` — auth: device-token.
+    `GET /api/sync/koreader/rating` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/get_rating.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/get_rating.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/get_review.yml

@@ -16,9 +16,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Get KOReader Review
+docs:
+  content: |-
+    # Get KOReader Review
 
-  `GET /api/sync/koreader/review` — auth: device-token.
+    `GET /api/sync/koreader/review` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/get_review.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/get_review.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/push_stats.yml

@@ -22,9 +22,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Push KOReader Stats
+docs:
+  content: |-
+    # Push KOReader Stats
 
-  `POST /api/sync/koreader/stats` — auth: device-token.
+    `POST /api/sync/koreader/stats` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/push_stats.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/push_stats.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/resolve_book.yml

@@ -16,9 +16,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Resolve Book:<|end|><|start|> assistant to=edit<|channel|>analysis <|constrain|>xml<|message|><rfl:parameter name="path">
+docs:
+  content: |-
+    # Resolve Book:<|end|><|start|> assistant to=edit<|channel|>analysis <|constrain|>xml<|message|><rfl:parameter name="path">
 
-  `GET /api/sync/koreader/resolve` — auth: device-token.
+    `GET /api/sync/koreader/resolve` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/resolve_book.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/resolve_book.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/set_rating.yml

@@ -22,9 +22,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Set KOReader Rating
+docs:
+  content: |-
+    # Set KOReader Rating
 
-  `POST /api/sync/koreader/rating` — auth: device-token.
+    `POST /api/sync/koreader/rating` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/set_rating.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/set_rating.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/set_review.yml

@@ -22,9 +22,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Set KOReader Review
+docs:
+  content: |-
+    # Set KOReader Review
 
-  `POST /api/sync/koreader/review` — auth: device-token.
+    `POST /api/sync/koreader/review` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/set_review.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/set_review.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/sync_bookmarks.yml

@@ -45,9 +45,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Sync Bookmarks
+docs:
+  content: |-
+    # Sync Bookmarks
 
-  `POST /api/sync/koreader/bookmarks` — auth: device-token.
+    `POST /api/sync/koreader/bookmarks` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/sync_bookmarks.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/sync_bookmarks.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown

bruno/koreader/sync_progress.yml

@@ -39,9 +39,11 @@ settings:
   followRedirects: true
   maxRedirects: 5
 
-docs: |-
-  # Sync Progress
+docs:
+  content: |-
+    # Sync Progress
 
-  `POST /api/sync/koreader/progress` — auth: device-token.
+    `POST /api/sync/koreader/progress` — auth: device-token.
 
-  Canonical reference: `docs/developer/api/koreader/sync_progress.md` (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, not this file.
+    Canonical reference: docs/developer/api/koreader/sync_progress.md (docs site → Developer → API). This request is GENERATED from that doc; edit the doc, then run the drift test with -update.
+  type: text/markdown