Reorganize ColdFront docs into the standard pgedge nav structure

.gitignore

@@ -24,6 +24,7 @@ REPO_READY_AUDIT.md
 
 # MkDocs build output
 site/
+.venv-docs/
 
 # pg_regress expected outputs — tracked; the global *.out would exclude them.
 !extension/coldfront/test/expected/*.out

CLAUDE.md

@@ -85,7 +85,7 @@ Snapshots of upstream state for the next major moves. Re-verify before acting on
 - duckdb-iceberg's 2.0-line commit path is rewritten (a retry loop with `RefreshFromCatalog` firing reactively after a 409, rather than proactively before the first attempt). Our bakery patch's anchors (`RefreshExistingManifestList`, `GetTransactionRequest`) no longer exist there — the proactive pre-commit refresh needs reimplementing, not dropping.
 - Two of our interop patches (manifest-list `format-version`, lowercase parquet `file_format`) are still needed against the 2.0-line `main`.
 - The DuckDB temp-spill collision above (`duckdb#15173`, `pg_duckdb#887`) is fixed on the 2.0 line: spill files are instance-qualified, so the per-backend temp directory stops being a correctness requirement once the stack moves to 2.0.
-- Partitioned `INSERT` and `CREATE TABLE ... PARTITIONED BY (...)` already work at our current `ICEBERG_REF`; `docs/architecture.md` and the extension's partition-column notice calling this unsupported are stale and should be corrected independently of the 2.0 move.
+- Partitioned `INSERT` and `CREATE TABLE ... PARTITIONED BY (...)` already work at our current `ICEBERG_REF`; `docs/architecture_guides/index.md` and the extension's partition-column notice calling this unsupported are stale and should be corrected independently of the 2.0 move.
 
 **DuckDB 1.5.6 (`v1.5-variegata` repin)** (checked 2026-10-04 at head `5dcf5070`): moving to the branch head forces a DuckDB newer than 1.5.4 for the whole stack — pg_duckdb loads extensions only for its exact DuckDB version, and pg_duckdb PR #1071 bumps to 1.5.5 while nothing upstream has tried 1.5.6 yet. All five `docker/iceberg-*-v15.patch` files still apply cleanly at the head and none of their fixes have landed upstream; `referenced_data_file` is still reader-only and `RETURNING` on a cold `INSERT`/`UPDATE`/`DELETE`/`MERGE` is still refused. The gains are vended-credential refresh, equality-delete scans with extra columns, truncated UTF-8 string bounds, an Azure SAS endpoint-suffix fix, and a `write.metadata.metrics` backport — treat a repin as a DuckDB stack move (base republish, full matrix), not a quick ref bump.
 
@@ -109,8 +109,8 @@ Snapshots of upstream state for the next major moves. Re-verify before acting on
 ## Documentation
 - User docs live in `docs/` as a MkDocs site (pgEdge MkDocs structure); `README.md` is the GitHub landing/TOC. Build with `mkdocs build --strict` — it must pass with no warnings.
 - Keep `README.md` and `docs/index.md` near-identical, EXCEPT `docs/index.md` is user-facing and omits the developer-specific content that belongs only in a GitHub README: CI badges, build-from-source internals, the project-structure tree, dependency/build tables, and author/contributor info.
-- Three indexes point at the pages in `docs/`, each with its own focus: the `mkdocs.yml` `nav:` (everything, including changelog, license and `formal/`), the `README.md` Documentation table (one terse row per guide), and the `docs/index.md` Next Steps list (prose, user-facing, top-level guides only; the per-mode deep dives are reached through `docs/architecture.md`, which lists them). Adding, renaming, or removing a guide under `docs/` means updating all three in the same commit; adding a deep dive means the nav, the README table, and the list in `docs/architecture.md`. `mkdocs build --strict` passes on a page no index links, so it will not catch this: check by listing `docs/*.md` against each index.
+- Three indexes point at the pages in `docs/`, each with its own focus: the `mkdocs.yml` `nav:` (everything, including changelog, license and `formal/`), the `README.md` Documentation table (one terse row per guide), and the `docs/index.md` Next Steps list (prose, user-facing, top-level guides only; the per-mode deep dives are reached through `docs/architecture_guides/index.md`, which lists them). Adding, renaming, or removing a guide under `docs/` means updating all three in the same commit; adding a deep dive means the nav, the README table, and the list in `docs/architecture_guides/index.md`. `mkdocs build --strict` passes on a page no index links, so it will not catch this: check by listing `docs/*.md` against each index.
 - Internal/scratch docs (bench, experimental, hardening, comparison, backlog, scale-test, E2E) are gitignored and NEVER pushed to GitHub; never reference them from published docs.
 - ARCHITECTURE docs are reference material, not work logs: brief, present-tense, no history ("we used to…", version churn), no rejected-alternative narration. Keep the *why* (rationale that explains the design); cut the journey.
-- One home per topic, no duplication across docs: usage/modes/config/CLI and one-time setup in `docs/usage.md`; build-from-source and testing/CI in `docs/installation.md`; storage-backend setup in `docs/object_store.md`; deep dives in `docs/architecture*.md`. When moving a section, fix every cross-anchor that pointed at it.
+- One home per topic, no duplication across docs: shared day-to-day usage and the partition CLI in `docs/using_coldfront/index.md`; each mode's own guide in `docs/usage_tiered.md`, `docs/usage_decoupled.md`, and `docs/usage_partitioner.md`; PostgreSQL/ColdFront config in `docs/configuration.md`; Lakekeeper install/config/bootstrap in `docs/configure_lakekeeper.md`; build-from-source and testing/CI in `docs/installation.md`; storage-backend setup in `docs/object_store.md`; deep dives in `docs/architecture_guides/index.md` and `docs/architecture_tiered.md`/`docs/architecture_decoupled.md`/`docs/architecture_vectors.md`. When moving a section, fix every cross-anchor that pointed at it.
 - Tracked build-journal docs (`DUCKDB_1.5_PATCHED.md`, `DUCKDB_1.5_UNPATCHED.md`) are kept as history and never deleted, but they are not part of the docs site: never link them from `README.md` or `docs/`. Point build internals at the real recipe, `docker/Dockerfile.duckdb15-base`.

CONTRIBUTING.md

@@ -5,8 +5,8 @@ Thanks for your interest in improving ColdFront.
 ## Getting started
 
 - Build and run the stack: [Installation](docs/installation.md).
-- Day-to-day usage and the two operating modes: [Usage](docs/usage.md).
-- Architecture: [Architecture](docs/architecture.md) (plus the tiered/decoupled
+- Day-to-day usage and the two operating modes: [Usage](docs/using_coldfront/index.md).
+- Architecture: [Architecture](docs/architecture_guides/index.md) (plus the tiered/decoupled
   deep dives).
 
 ## Development workflow