docs(changelog): quote both diagnostics — the old one, and the line it now carries

The Unreleased entry for the placeholder fix described the new sentence but
never showed either message, so a reader could not tell what actually changed
in the output. It now quotes both forms verbatim, and names the command they
were captured from:

    go run ./cmd/oh-my-graph run /tmp/omg-repro-placeholder.yaml --dry-run

Old (209df64^, internal/handoff/handoff.go:146 and :170):

    cannot resolve {{ inputs.demo }}: no such input was provided
    cannot resolve {{ artifacts.nosuch }}: artifact not available (its
    producing node has not completed)

New (handoff.go:159 and :183, the quotingHint constant at :56):

    cannot resolve {{ inputs.demo }}: no such input was provided
    note: every {{ ... }} in a prompt is resolved, including one that is only
    being quoted or explained — to keep such text literal, break the two
    braces apart ("{ {"), or pass the text in as an input or artifact instead
    of writing it in the prompt

The quoted text was read back off the running binary, not copied from the
implementation report. CHANGELOG.md only — no code, no release, no tag, no
version bump.

Signed-off-by: jitokim <pigberger70@gmail.com>
Co-Authored-By: oh-my-graph <graphs@oh-my-graph.dev>

Author: jitokim

CHANGELOG.md

@@ -17,11 +17,35 @@ oh-my-graph is **alpha software**. The graph YAML schema, the CLI, and the
   reasons were written as if the graph had meant the token — the artifact one
   asserts "its producing node has not completed" about a node that may not
   exist — so a prompt that only explains the syntax to the model got a
-  diagnostic pointing at wiring that was never there. Both errors gain one
-  line: every `{{ ... }}` in a prompt is resolved, including one only being
-  quoted or explained; to keep such text literal, break the two braces apart
-  (`{ {`) or pass the text in as an input or artifact. Wording only — no
-  escaping syntax, no flag, and interpolation itself is unchanged.
+  diagnostic pointing at wiring that was never there.
+
+  Before, both errors said only what was missing:
+
+  ```
+  cannot resolve {{ inputs.demo }}: no such input was provided
+  cannot resolve {{ artifacts.nosuch }}: artifact not available (its producing node has not completed)
+  ```
+
+  After, each carries a second line stating the rule and the way out:
+
+  ```
+  cannot resolve {{ inputs.demo }}: no such input was provided
+  note: every {{ ... }} in a prompt is resolved, including one that is only being quoted or explained — to keep such text literal, break the two braces apart ("{ {"), or pass the text in as an input or artifact instead of writing it in the prompt
+  ```
+
+  The artifacts form gains the same single line after `artifact not available
+  (its producing node has not completed)`. The command those two captures came
+  from is the address for them — a graph whose prompts only *mention* the
+  syntax:
+
+  ```sh
+  go run ./cmd/oh-my-graph run /tmp/omg-repro-placeholder.yaml --dry-run
+  ```
+
+  Appended at exactly those two sites and nowhere else: a filter on a feedback
+  token and an unreadable artifact file are real wiring bugs, where this advice
+  would mislead. Wording only — no escaping syntax, no flag, and what
+  `Interpolate` resolves is unchanged.
 
 - **`runs list` collapses the per-run skip warnings into one summary line, and
   the detail moves behind `--show-skipped`.** Option chosen: *collapse by