docs: reorganize documentation and reset release history to the fork

Rework the documentation into a clearer structure and remove content that
does not apply to open_pg_tde.

Structure:
- Move internal design docs from docs/design/ to a repo-root design/ directory
  so the repo no longer has both docs/ and documentation/ at the root.
- Rename site folders to describe their contents: index/ -> concepts/,
  global-key-provider-configuration/ -> key-management/,
  advanced-topics/ -> reference/. Update all internal links and the README.
- Rebuild the nav: drop numeric prefixes, add the previously orphaned
  contribute and pg-tde-upgrade pages, and point the README at the published
  site instead of the documentation/ directory tree.

Release notes:
- Remove the pre-fork Percona pg_tde lineage (MVP through 2.2.1). open_pg_tde's
  history starts at 2.3.0. Update variables.yml and the index accordingly.

Consolidation:
- Merge usage-guide into functions.md, restore-backups into backup-wal-enabled,
  the three KMIP vendor stubs into kmip-servers, supported-versions into
  install, and documentation-contributing into contribute. Delete tech-reference.

Cleanup:
- Remove dead assets (rating widget, promptremover.js, missing version-select.js
  reference, postgresql.css, Percona icon, unused SCSS) and prune requirements.

Accuracy:
- Fix the default cipher (AES-128-XTS, not CBC), the KMIP parameter order, the
  temp-file encryption description, the inherit_global_providers GUC name, the
  impact-table icons, the pg_stat_monitor example, and several typos.

mkdocs build --strict passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: OffgridwithJD

CONTRIBUTING.md

@@ -95,4 +95,4 @@ Maintainers cutting a release build one source tarball per supported PostgreSQL
 
 ## Documentation contribution
 
-To contribute to the documentation, see the [documentation contributing guide](documentation/documentation-contributing.md).
+To contribute to the documentation, see the [contributing guide](documentation/docs/contribute.md).

README.md

@@ -25,15 +25,15 @@ required.
 
 > `open_pg_tde` is an open fork of `pg_tde`,
 > maintained by [Command Prompt, Inc.](https://www.commandprompt.com/) See how
-> they differ in the [comparison with pg_tde](documentation/docs/index/comparison-percona.md).
+> they differ in the [comparison with pg_tde](documentation/docs/concepts/comparison-percona.md).
 
 ## Features
 
 - **Per-table encryption** with the `tde_heap` access method. The cipher is
   recorded per table, so encrypted and plain tables coexist.
 - **Encrypted at rest:** table data, indexes, TOAST, the WAL, and temporary
   (query-spill) files. System catalogs and statistics are not encrypted; see the
-  [threat model](documentation/docs/index/threat-model.md).
+  [threat model](documentation/docs/concepts/threat-model.md).
 - **Data ciphers:** AES-128-XTS (default), AES-256-XTS, AES-128-CBC, and
   AES-256-CBC, selected with [`open_pg_tde.data_cipher`](documentation/docs/variables.md).
   The WAL uses AES-CTR.
@@ -42,7 +42,7 @@ required.
   [OpenBao](https://openbao.org/) as providers, per database or cluster-wide.
 - **FIPS:** all cryptography runs through OpenSSL with FIPS-approved modes, and
   the server can be required to start only in OpenSSL FIPS mode. See
-  [FIPS compliance](documentation/docs/index/fips.md).
+  [FIPS compliance](documentation/docs/concepts/fips.md).
 - **Upstream PostgreSQL:** a gated core patch adds the storage-manager and WAL
   hooks. With the flag off, the tree builds as unmodified PostgreSQL.
 
@@ -53,7 +53,7 @@ required.
 | 18 | Supported |
 | 17 | Supported |
 | 16 | Supported (minimum) |
-| 19 | Beta port in progress ([roadmap](docs/design/encryption-roadmap.md#postgresql-version-support)) |
+| 19 | Beta port in progress ([roadmap](design/encryption-roadmap.md#postgresql-version-support)) |
 
 ## Installation
 
@@ -93,17 +93,19 @@ encryption, and enabling encryption by default.
 
 ## Documentation
 
-The full documentation source is in [`documentation/`](documentation/).
+The full documentation is published at
+**[commandprompt.github.io/open_pg_tde](https://commandprompt.github.io/open_pg_tde/)**.
+The Markdown source lives in the `documentation/` directory of this repository.
 
 | | |
 | --- | --- |
 | [Setup and configuration](documentation/docs/setup.md) | Install, key providers, encrypted tables |
-| [Key management](documentation/docs/global-key-provider-configuration/overview.md) | Keyring file, KMIP, OpenBao |
+| [Key management](documentation/docs/key-management/overview.md) | Keyring file, KMIP, OpenBao |
 | [GUC variables](documentation/docs/variables.md) | All settings |
 | [Functions](documentation/docs/functions.md) | Helper functions |
-| [Threat model](documentation/docs/index/threat-model.md) | What encryption at rest does and does not protect |
-| [FIPS compliance](documentation/docs/index/fips.md) | Approved algorithms and FIPS mode |
-| [Comparison with Percona pg_tde](documentation/docs/index/comparison-percona.md) | How the fork differs |
+| [Threat model](documentation/docs/concepts/threat-model.md) | What encryption at rest does and does not protect |
+| [FIPS compliance](documentation/docs/concepts/fips.md) | Approved algorithms and FIPS mode |
+| [Comparison with Percona pg_tde](documentation/docs/concepts/comparison-percona.md) | How the fork differs |
 
 ## Contributing