(feat) Discord build share

docs/DESIGN_SYSTEM.md

@@ -1920,10 +1920,33 @@ selector:
 - `PUBLIC` is accessible by direct link and included in the public archive.
 
 Keep visibility adjacent to the account-save action and explain its selected
-state in plain language. Show a share-page action only after a non-private build
-has been saved. Public and unlisted build pages are read-only tactical
-summaries; owner editing returns to the builder. On narrow layouts, persistence
-controls and shared-loadout columns stack vertically.
+state in plain language. Show Build Uplink after an Agent saves a Build. Public
+and unlisted Builds expose its active controls; private Builds show the locked
+state. Public and unlisted Build pages are read-only tactical summaries; owner
+editing returns to the builder.
+
+Build Uplink uses a compact tactical control surface. Use one bordered dark
+panel with a raised telemetry header, a textual `PUBLIC LINK READY` or
+`UNLISTED LINK READY` state, and a small orange signal marker. The primary
+`SHARE BUILD` action opens the native Web Share sheet when the browser supports
+it. Keep `COPY LINK` visible as a separate explicit action for every eligible
+Build. When Web Share is unavailable, promote Copy Link to the primary action
+instead of presenting a control that cannot run. Supporting copy may state that
+Discord renders the Build preview after an Agent posts the link. It must not
+imply that SHD.build posts to Discord or operates a bot.
+
+Private and unsaved Builds use the locked Uplink state. Show `PRIVATE BUILD` or
+`UNSAVED BUILD`, `PUBLIC LINK UNAVAILABLE`, and a short instruction to change
+visibility or save. Render no active Share or Copy Link control in that state.
+Do not expose a crawler-preview action or suggest that owner access makes a
+private Build shareable.
+
+Uplink actions retain textual pending, success, cancellation, unsupported, and
+failure feedback. They use at least 44-pixel targets, orange focus-visible
+treatment, pressed feedback, and disabled duplicate-action protection. Stack
+Share above Copy Link at phone widths and remove pressed motion under
+`prefers-reduced-motion`. On narrow layouts, persistence controls and
+shared-loadout columns also stack vertically.
 
 ### Tiered compatibility editors
 

docs/architecture.md

@@ -187,6 +187,40 @@ boundary. An owned Build page links to `/guides/new?build=<id>`, where the
 server verifies ownership and initializes a removable Build block in a new
 private Guide.
 
+### Discord-compatible Build sharing experiment
+
+Persisted public and unlisted Builds expose absolute Open Graph metadata for
+their canonical `/builds/[slug]` URL. Their `og:image` and Twitter card metadata
+reference the same-origin 1200 × 630 PNG at `/builds/[slug]/preview.png` so
+Discord and other link unfurlers can render a Build summary. Private Builds set
+`noindex,nofollow`, expose no crawler image, and provide no usable sharing
+control.
+
+The preview endpoint derives its image from canonical Build facts and the
+current known-stat summary in the shared Build projection. It includes the Build
+title, author, visibility, direct URL, equipped weapon names, core totals, and
+up to three supporting Attributes. The renderer performs no external fetches. It
+normalizes and bounds every text field by grapheme count, escapes text before
+inserting it into XML, builds a text-only SVG, and rasterizes that SVG to PNG
+with Sharp. Production installs DejaVu Sans from the Debian package and the
+renderer names that fixed family explicitly.
+
+The endpoint hashes a versioned serialization of the image input for its bounded
+in-process render cache and derives the HTTP ETag from the resulting PNG bytes.
+A bounded request queue limits concurrent database projections and Sharp work.
+Responses require cache revalidation so a visibility change to Private blocks
+the next request instead of leaving a stale response window. Matching
+conditional requests receive `304 Not Modified`. Private, missing, and
+inaccessible Builds receive no preview. Unlisted images send the
+`X-Robots-Tag: noindex` response header.
+
+For eligible Builds, the Build Uplink invokes the native Web Share API as the
+primary action when the browser supports it. An explicit Copy Link action
+remains available for every public or unlisted persisted Build. This experiment
+does not install a Discord bot, post to Discord, extend Discord OAuth scopes, or
+store Discord tokens or webhooks. Discord receives only a link that an Agent
+chooses to share and may fetch the public metadata and same-origin preview.
+
 ## Public data corrections and discussion
 
 Every public database card links to its canonical ISAC record with an exact