Use only plain characters inside sequence diagram messages

GoLand's Mermaid preview renders the flowchart and state diagrams but not
two of the sequence diagrams. Remove "|", "||", "+" and braces from message
text, the only characters those diagrams had that the others lack.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/enrollment-and-activation.md

@@ -46,14 +46,14 @@ sequenceDiagram
     participant G as Go backend
     B->>B: random Client ID, X25519 keypair (b, B), nonce n1
     B->>M: CONNECT (TLS, anonymous, clientId=random)
-    B->>G: enroll/request/{cid} {B, n1, mac}
+    B->>G: enroll/request/[cid] [B, n1, mac]
     G->>G: create FN record, ephemeral (s, S)
     G->>G: shared = X25519(s, B), pw = HKDF(shared, FN, n1)
     G->>M: Dynamic Security: create client FN, pw, role board-bootstrap
-    G->>B: enroll/response/{cid} {FN, S, sig}  (not retained)
+    G->>B: enroll/response/[cid] [FN, S, sig]  (not retained)
     B->>B: verify sig with pinned public key
     B->>B: shared = X25519(b, S), same pw
-    B->>B: persist FN + pw to flash
+    B->>B: persist FN and pw to flash
     B->>M: reconnect as FN / pw
 ```
 
@@ -94,13 +94,13 @@ sequenceDiagram
     participant G as Go backend
     participant M as Mosquitto
     participant B as Board (FN)
-    B->>G: board/{FN}/activation/request
+    B->>G: board/[FN]/activation/request
     O->>G: pick SN, confirm code and short string
-    G->>M: ensure role machine-{SN} (literal ACLs device/{SN}/...)
+    G->>M: ensure role machine-[SN] (literal ACLs device/[SN]/...)
-    G->>M: add roles machine-{SN} + capability roles to client FN
+    G->>M: add roles machine-[SN] + capability roles to client FN
-    G->>B: board/{FN}/activation/response {SN, sig}
+    G->>B: board/[FN]/activation/response [SN, sig]
     B->>B: store SN, reconnect as FN
-    B->>M: use device/{SN}/... topics
+    B->>M: use device/[SN]/... topics
 ```
 
 - **Roles:** one assignment role per machine, `machine-<SN>`, with **literal** topics such as `device/SN000123/sales/report`. `%u` cannot express the SN here because the username is the FN. Plus shared capability roles (`vending`, `news`, `updates`).
@@ -119,12 +119,12 @@ sequenceDiagram
     participant M as Mosquitto
     participant B as Board (FN)
     B->>B: new ephemeral X25519 keypair (b2, B2)
-    B->>G: board/{FN}/activation/request {B2, n2}
+    B->>G: board/[FN]/activation/request [B2, n2]
     O->>G: pick SN, confirm code and short string
     G->>G: ephemeral (s2, S2), shared = X25519(s2, B2)
     G->>G: pw = HKDF(shared, SN, n2, generation)
     G->>M: create or update client SN: pw, clientId bound to board, role vending-device
-    G->>B: board/{FN}/activation/response {SN, S2, sig}
+    G->>B: board/[FN]/activation/response [SN, S2, sig]
     B->>B: verify sig, derive same pw, store SN + pw
     B->>M: reconnect as SN / pw
     G->>M: disable FN client (or keep for rescue / re-enrollment)

docs/sn-as-username-process.md

@@ -118,14 +118,14 @@ sequenceDiagram
     participant G as Go backend
     B->>B: random Client ID, X25519 pair (b, B), nonce n1
     B->>M: CONNECT anonymous, clientId=random (TLS)
-    B->>M: SUBSCRIBE enroll/response/{cid}  (own topic only)
+    B->>M: SUBSCRIBE enroll/response/[cid]  (own topic only)
-    B->>G: enroll/request/{cid} {B, n1, mac}
+    B->>G: enroll/request/[cid] [B, n1, mac]
-    G->>G: reserve {cid}, assign FN, ephemeral (s, S)
+    G->>G: reserve [cid], assign FN, ephemeral (s, S)
-    G->>G: shared = X25519(s, B), pw = HKDF(shared, salt=n1, info=label|FN)
+    G->>G: shared = X25519(s, B), pw = HKDF(shared, salt=n1, info = label, FN)
     G->>M: dynsec createClient FN, pw, clientid=FN, role board-bootstrap
-    G->>B: enroll/response/{cid} {FN, S, sig}  (not retained)
+    G->>B: enroll/response/[cid] [FN, S, sig]  (not retained)
     B->>B: verify sig, shared = X25519(b, S), same pw
-    B->>B: persist FN + pw to flash, then reconnect as FN
+    B->>B: persist FN and pw to flash, then reconnect as FN
 ```
 
 - `sig` = Ed25519 over `S || B || n1 || clientid || FN`. Binding the FN and the Client ID means a reply for another request, board or identity does not verify.
@@ -161,17 +161,17 @@ sequenceDiagram
     participant G as Go backend
     participant M as Mosquitto
     participant B as Board (FN session)
-    B->>B: fresh X25519 pair (b2, B2), nonce n2, SAS = digits(hash(B2 || n2 || FN))
+    B->>B: fresh X25519 pair (b2, B2), nonce n2, SAS = digits(hash(B2, n2, FN))
-    B->>G: board/{FN}/activation/request {B2, n2}
+    B->>G: board/[FN]/activation/request [B2, n2]
     G->>O: pending request FN, MAC label, SAS, time
     O->>G: choose SN, enter activation code, confirm SAS matches the board
-    G->>G: DB: ACTIVATING (FN, SN, generation g+1), unique constraint
+    G->>G: DB: ACTIVATING (FN, SN, next generation), unique constraint
-    G->>G: ephemeral (s2, S2), shared2, pw_sn = HKDF(shared2, salt=n2, info=label|SN|g+1)
+    G->>G: ephemeral (s2, S2), shared2, pw_sn = HKDF(shared2, salt=n2, info = label, SN, generation)
     G->>M: dynsec create or update client SN: pw_sn, role vending-device, clientid = FN
-    G->>B: board/{FN}/activation/response {SN, g+1, S2, sig}
+    G->>B: board/[FN]/activation/response [SN, next generation, S2, sig]
-    B->>B: verify sig, derive pw_sn, persist SN + pw_sn + generation, reconnect
+    B->>B: verify sig, derive pw_sn, persist SN, pw_sn and generation, reconnect
     B->>M: CONNECT username=SN, clientId=FN, password=pw_sn
-    M-->>G: first message on device/{SN}/... (or presence)
+    M-->>G: first message on device/[SN]/... (or presence)
     G->>G: DB: ACTIVE, disable the FN client, audit
 ```