O1b-1c: bind closed absence to host identity (#481)

Make point attachment admission closed-by-construction, bind authority to an immutable host epoch, and let Core mint exact mutation successors. Preserve retryable cold failures and keep the public API unchanged.

Author: lemone112

crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.json

@@ -69,25 +69,25 @@
       "sha256": "ec6585496208972e183d3a5bcd1f67bae4d89cc8e6a797d9c6443d8e0754502b"
     },
     {
-      "bytes": 37562,
+      "bytes": 46758,
       "license": "MIT",
       "path": "crates/labcolors-core/src/program/attachment.rs",
       "role": "point_attachment_source",
-      "sha256": "b1bb2f4c25e748ba7c3711454e968bca24ed934f18f00ccdca4a1a2c572bceb7"
+      "sha256": "721fa5852a400184908a2751f2caab782d6a88cb16bf6e64d5ff0f4d4867fc74"
     },
     {
-      "bytes": 17406,
+      "bytes": 25241,
       "license": "MIT",
       "path": "crates/labcolors-core/src/program/attachment/support.rs",
       "role": "point_attachment_test_support",
-      "sha256": "df2350e853302ffb636abf01d7c1301331fc76f4708ca00d076ea91dac0b14bb"
+      "sha256": "2ea5dc94f3a101428947ad34dc64cb9fbc7a5a7b666b6795ab837540f98aa7e1"
     },
     {
-      "bytes": 31748,
+      "bytes": 54584,
       "license": "MIT",
       "path": "crates/labcolors-core/src/program/attachment/tests.rs",
       "role": "point_attachment_tests",
-      "sha256": "6ea55c62333a803929fd4b96245362148a555ca2ac5261721a6fad6de9bf7eac"
+      "sha256": "1a45dafe529c0855b7cabc054b94d096c661e81243d2a80d78f740bcb595d105"
     },
     {
       "bytes": 162073,

crates/labcolors-core/contracts/clean-set-srgb8-v1/receipt-v1.sha256

@@ -1 +1 @@
-369e1cf175ac10ab96ca1f6cb82e131e4c24fc43c698a0d853ccabdebb0386d5  receipt-v1.json
+644195947c48b841dd319e7586700986ddf4fd4553d593d093c4e109a3002fe3  receipt-v1.json