docs: comprehensive documentation audit — fix stale info, expand thin pages, add depth (#5393)

Major changes across 20 documentation pages:

Staleness fixes:
- Fix FAQ: wrong import path (hermes.agent → run_agent)
- Fix FAQ: stale Gemini 2.0 model → Gemini 3 Flash
- Fix integrations/index: missing MiniMax TTS provider
- Fix integrations/index: web_crawl is not a registered tool
- Fix sessions: add all 19 session sources (was only 5)
- Fix cron: add all 18 delivery targets (was only telegram/discord)
- Fix webhooks: add all delivery targets
- Fix overview: add missing MCP, memory providers, credential pools
- Fix all line-number references → use function name searches instead
- Update file size estimates (run_agent ~9200, gateway ~7200, cli ~8500)

Expanded thin pages (< 150 lines → substantial depth):
- honcho.md: 43 → 108 lines — added feature comparison, tools, config, CLI
- overview.md: 49 → 55 lines — added MCP, memory providers, credential pools
- toolsets-reference.md: 57 → 175 lines — added explanations, config examples,
  custom toolsets, wildcards, platform differences table
- optional-skills-catalog.md: 74 → 153 lines — added 25+ missing skills across
  communication, devops, mlops (18!), productivity, research categories
- integrations/index.md: 82 → 115 lines — added messaging, HA, plugins sections
- cron-internals.md: 90 → 195 lines — added job JSON example, lifecycle states,
  tick cycle, delivery targets, script-backed jobs, CLI interface
- gateway-internals.md: 111 → 250 lines — added architecture diagram, message
  flow, two-level guard, platform adapters, token locks, process management
- agent-loop.md: 112 → 235 lines — added entry points, API mode resolution,
  turn lifecycle detail, message alternation rules, tool execution flow,
  callback table, budget tracking, compression details
- architecture.md: 152 → 295 lines — added system overview diagram, data flow
  diagrams, design principles table, dependency chain

Other depth additions:
- context-references.md: added platform availability, compression interaction,
  common patterns sections
- slash-commands.md: added quick commands config example, alias resolution
- image-generation.md: added platform delivery table
- tools-reference.md: added tool counts, MCP tools note
- index.md: updated platform count (5 → 14+), tool count (40+ → 47)

website/docs/user-guide/features/context-references.md

@@ -95,6 +95,38 @@ All paths are resolved relative to the working directory. References that resolv
 
 Binary files are detected via MIME type and null-byte scanning. Known text extensions (`.py`, `.md`, `.json`, `.yaml`, `.toml`, `.js`, `.ts`, etc.) bypass MIME-based detection. Binary files are rejected with a warning.
 
+## Platform Availability
+
+Context references are primarily a **CLI feature**. They work in the interactive CLI where `@` triggers tab completion and references are expanded before the message is sent to the agent.
+
+In **messaging platforms** (Telegram, Discord, etc.), the `@` syntax is not expanded by the gateway — messages are passed through as-is. The agent itself can still reference files via the `read_file`, `search_files`, and `web_extract` tools.
+
+## Interaction with Context Compression
+
+When conversation context is compressed, the expanded reference content is included in the compression summary. This means:
+
+- Large file contents injected via `@file:` contribute to context usage
+- If the conversation is later compressed, the file content is summarized (not preserved verbatim)
+- For very large files, consider using line ranges (`@file:main.py:100-200`) to inject only relevant sections
+
+## Common Patterns
+
+```text
+# Code review workflow
+Review @diff and check for security issues
+
+# Debug with context
+This test is failing. Here's the test @file:tests/test_auth.py
+and the implementation @file:src/auth.py:50-80
+
+# Project exploration
+What does this project do? @folder:src @file:README.md
+
+# Research
+Compare the approaches in @url:https://arxiv.org/abs/2301.00001
+and @url:https://arxiv.org/abs/2301.00002
+```
+
 ## Error Handling
 
 Invalid references produce inline warnings rather than failures: