…onal behavior

Backfill 14 golden specs (plus README + template) describing what the system
does today, paired with the existing decisions/ ADRs that explain why.

Each spec follows: Purpose, user stories (human + AI agent), numbered
functional requirements, non-functional requirements, current-implementation
file pointers, future work tied to a tracking issue or ADR.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

…sion

Naming a specific Chrome version (148+) freezes the spec to the build at
authoring time; the actual intent is "latest stable Chromium release," with
the manifest's minimum_chrome_version tracking that baseline.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

- 0013 FR-4: storage key is `agent-browser-shield.openai-api-key`, not
  `agent-browser-shield.api-key`.
- 0009 FR-2: drop the stale 15-host enumeration (the directory ships 80
  YAMLs); defer to `extension/data/sites/*.yaml` as authoritative and add a
  category sketch.
- 0005 FR-3 / FR-4: quote the full cart-addon and hidden-fee chip
  templates including the parenthetical match info and the verify-before
  -completing directive — the actual chip is materially longer than the
  short `[abs: …]` prefix the spec was showing.
- 0004 FR-3 (and the matching user story): show the real label format
  (`[card hidden]`, `[secret hidden]`, …) rather than the stylized
  `credit card` / `secret` examples that don't appear anywhere in the
  rendered placeholders.
- 0008 FR-5: replace the paraphrased "may contain content ABS cannot
  see" quote — which matches an in-code comment but not the actual
  landmark — with a direct quote of the user-visible `LANDMARK_TEXT`.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Each spec now carries a Problem section between Purpose and User stories,
naming the harm, friction, or risk the capability exists to address. The
Problem answers "what would go wrong without this?" — the *product* why —
in contrast to ADRs, which carry the *implementation* why (path chosen
over alternatives).

- specs/_template.md: new Problem section in the template with guidance
  on scope (product why, not implementation why).
- specs/README.md: spec-vs-ADR distinction rewritten to acknowledge both
  kinds of doc carry a "why" — specs the product why, ADRs the
  implementation why; section-order list updated to include Problem.
- specs/0001..0014: each spec gains a Problem paragraph derived from the
  capability's reason-to-exist: e.g. 0003 names indirect prompt injection
  bypassing prompt-layer filtering; 0004 names PII/credentials silently
  shipped into model context; 0006 names token-budget burn from page
  chrome; 0008 names invisible coverage gaps being worse than no
  coverage; 0013 names the inverted trust model if a defense extension
  itself leaks data.

No FR/NFR changes; existing citations remain backed by the same code.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>