feat(web): idx website and user docs (Astro Starlight)

Landing page plus docs for install, quickstart, config, the stocks and
ownership CLI, output and exit codes, the MCP server and per-agent setup,
agent usage, and an agent-led install page (agents/install.md) that a
coding agent follows from a one-line prompt.

- Every docs page is also served as Markdown at <path>.md; llms.txt and
  llms-full.txt come from starlight-llms-txt; a SKILL.md for skill-based
  harnesses is under /skills/idx/.
- The CLI reference and MCP tools pages are generated from idx --help and
  the tools golden; a new web-generated flake check fails when they drift.
- nix develop .#web provides bun; Cloudflare Pages builds web/ on pushes.
- Package homepage metadata points at https://idx.rasyidanaf.com.
- .cloudflare/ (the cf CLI's account cache) is git-ignored.

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

web/src/content/docs/cli/ownership.md

@@ -0,0 +1,57 @@
+---
+title: Ownership
+description: KSEI shareholder data, synced once and queried offline.
+---
+
+The ownership commands work on the monthly KSEI register of holders above 1%
+("Pemegang Saham di Atas 1%") that IDX publishes for every listed company.
+idx keeps it in a local SQLite database, so queries are instant and work
+offline.
+
+## Get the data
+
+```bash
+idx ownership sync
+```
+
+This downloads a maintained snapshot (a few MB, currently the latest three
+months) and installs it. Run it again any time: it does nothing when you are
+already current, and it never replaces a database holding more history than
+the snapshot. `idx ownership releases` lists the months you have.
+
+## Queries
+
+```bash
+idx ownership ticker BBCA               # holders of one stock, with concentration
+idx ownership entity "ANTHONI SALIM"    # every holding of one investor
+idx ownership search salim              # find investor names
+idx ownership changes --from 2026-08-31 --to 2026-09-30
+idx ownership concentration --top 20    # most concentrated stocks (by HHI)
+idx ownership cross-holders --min-tickers 3
+idx ownership graph BBCA --depth 2      # ownership network; --format dot for Graphviz
+```
+
+`changes` lists holders that are new, exited, increased or decreased between
+two releases. `ticker` also reports concentration: the top holder's share,
+the top three, the Herfindahl index (HHI) and the free float (shares held by
+holders below 1%).
+
+## Import reports yourself
+
+The snapshot covers most needs. To load a month it lacks, or older history,
+import IDX's reports directly:
+
+```bash
+idx ownership discover                     # find the latest report URLs on IDX
+idx ownership import --url <xlsx-or-pdf>   # needs curl-impersonate
+idx ownership import --file report.xlsx    # or a local XLSX, PDF, ZIP or TXT
+```
+
+Since June 2026 IDX publishes the register as XLSX; earlier months were PDF
+announcements, which need `mutool`. See [helper tools](/start/install/#helper-tools).
+
+## Entity names
+
+The register spells some investors differently from month to month.
+`idx ownership resolve` lists unresolved names and lets you map an alias to
+an entity or merge two entities.