skills: publish the index, leave the body on disk

the inverse of an affordance, and deliberately so:

  affordance   body always compiled in, description never sent
  skill        description always compiled in, body read on demand

an affordance is a fact about the surface — short, and every conversation
needs it. a skill is reference material that is dead weight in a conversation
about something else. so what reaches the prompt is the index: name, when to
reach for it, and the path. measured on the first one: 608 characters in the
prompt against 6,070 bytes left on disk.

no protocol. progressive disclosure is normally a harness feature — claude
code discovers .claude/skills, opencode has its own conventions, the next one
will have a third — and pointing at a file needs none of that, because every
harness worth running can already read a file. the cost is that the agent has
to CHOOSE to open it, which is what the description is for and why a vague one
makes a skill useless rather than merely verbose.

the first skill is the email database, moved out of tools/email-db/TOOL.md
where NOTHING has been reading it: the loader parses frontmatter and discards
the body, so that schema and its eight queries have never reached any claude
code session. written for pi, inert since pi left.

it carries two things the schema alone gets wrong, both measured against the
real 19,097-message database rather than copied from the old doc: `read` is
populated on 93 rows, so the documented unread query returns essentially the
whole mailbox; and `labels` is a comma-separated string with real values like
`updates,inbox`, so `labels = 'inbox'` misses most of the inbox.

plugins can ship skills, published and unpublished on install like affordances
and notification catalogues. flat namespace unlike those two — a skill's
directory name is the path an agent reads, and `officerdev/gitea/SKILL.md` in
a prompt is noise. a skill has no authority to usurp, so nothing needs
protecting.

wired to claude code. opencode still gets NOTHING — its runner sends no system
prompt at all, and session create takes only a directory. that needs its own
channel and a guess would be worse than the gap.

src/servers/sidecar/claude/claude-manager.ts

@@ -5,6 +5,7 @@ import { join } from 'node:path';
 import { query, type Query, type SpawnOptions, type SpawnedProcess } from '@anthropic-ai/claude-agent-sdk';
 import type { ChatEvent, PromptImage } from '../../api/chat/types';
 import { affordanceBlock } from '../../affordances/load';
+import { skillsBlock } from '../../skills/load';
 import type { ClaudeSpawnParams, ClaudeSpawnStreamingParams, ClaudeCodeResult, LiveClaudeSession } from '../protocol';
 import { setClaudeSession, clearClaudeSession, getClaudeSession } from './state';
 import { countsAsOutput, diagnoseExit, stderrReason } from './exit-diagnosis';
@@ -579,6 +580,11 @@ function createSession(
   // Read here rather than at module load: a plugin installed an hour ago should be live on the next
   // message, and this costs a few kilobytes once per session.
   const affordances = affordanceBlock();
+  // The skills INDEX — names, descriptions and paths, never bodies. See skills/load.ts for why this is
+  // the inverse of an affordance. Read here rather than at module load for the same reason: a skill
+  // written an hour ago should be offered on the next session.
+  const skills = skillsBlock();
+  const preamble = [affordances, skills].filter(Boolean).join('\n\n') || null;
 
   const q = query({
     prompt: input.gen as AsyncIterable<SdkUserMessage>,
@@ -711,8 +717,8 @@ function createSession(
        * holds on one harness is the drift this exists to remove. Deliberate as of 2026-08-19: opencode
        * development is paused pending its v2 migration, so the work would be thrown away. See TODO.md.
        */
-      ...(affordances
-        ? { systemPrompt: { type: 'preset' as const, preset: 'claude_code' as const, append: affordances } }
+      ...(preamble
+        ? { systemPrompt: { type: 'preset' as const, preset: 'claude_code' as const, append: preamble } }
         : {}),
       env: cleanEnv as Record<string, string>,
       stderr: (d: string) => {