chore: fix user-facing and comment typos (reciever, seperator, occured)

[SAY-5]

Summary

Seven typos across four files; two surface to users via HCL JSON parser diagnostics:

• json/parser.go — `Missing attribute seperator comma` (two spots) → `separator`
• json/public.go — `an error occured while closing/reading it.` → `occurred`

Comment-only fixes:

• diagnostic.go — `recieve` → `receive`, `reciever` → `receiver`
• pos.go — `reciever` → `receiver` (×3)
• hclwrite/node.go — `reciever` → `receiver`

Test plan

• go build ./...
• go vet ./...
• go test ./... -count=1 -timeout 120s — full suite green, including hclwrite/fuzz, integrationtest, json, json/fuzz, specsuite

[hashicorp-cla-app]

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[hashicorp-cla-app]

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[crw]

Thanks for this submission. We generally do not take typo fix PRs unless changes are already being made to the files in question.